Secure and Reliable Energy Harvesting System Design for Sustainability in IoT for Smart Cities and Smart Villages

Abstract

The Internet-of-Things (IoT) consists of a large number of different and heterogeneous devices under one umbrella. Building a typical architecture for the devices used in IoT is a challenge due to the involvement of a vast number of devices, layers, protocols, middleware, and software. The sensors in IoT have to monitor the activities regularly, making the end node devices energy hungry. Traditional fixed batteries get drained out in a limited time, requiring continuous replacement, thereby increasing the budget. Providing power to IoT things (i.e., sensors + their communications) is a challenge as batteries have a limited lifetime and maintenance, and disposal is costly and hazardous. System on chip (SoC) power requirements for IoT ultra-low-power realm are different and needs a lot of effort for the design engineers to provide uninterrupted power. The power requirements also include power conditioning in generating higher voltages on-chip, which is a massive challenge for on-chip peripherals and systems. Recently, harvesting natural energy is gaining more attention than other conventional approaches for sustainable Internet-of-Things (IoT). To face the challenges in current IoTs, the focus should also be on security and reliability in energy harvesting system (EHS) design. Security, reliability and energy consumption are the conflicting challenges in the design and operation as per the application requirements in IoT. A detailed discussion is carried out in selecting a appropriate energy source and power conditioning circuits suitable for on-chip implementation. The switched capacitor (SC) circuits are proved to be more beneficial for on-chip performance and to extract maximum power from the input. Hill-climbing and perturb & observe maximum power point tracking (MPPT) techniques are chosen due to their inherent advantages in extracting maximum power from the source. The proposed charge pump (CP) uses a two-phase clock with adiabatic-charging and charge-sharing principle, with separate body bias. The independent body bias of higher amplitude resolves the threshold voltage issues and the reverse current problem. This principle also reduces the charge transfer and charge-sharing losses. The control section monitors the load and also the recharging of the battery/super-capacitor. Low drop-out regulators (LDOs) are used to provide various regulated power to the load. In this thesis, a paradigm shift research that addresses secure self-sustainable solar energy harvesting system (EHS) with security and reliability mechanism is proposed. This design incorporates unique ID generation of a device, physically unclonable functions (PUFs) for the protection of EHS by enabling various modules along with a mechanism to detect recycled IC. Many reliability degrading factors influence the performance of EHS which includes ripples and attacks due to adversaries. The presence of ripples, intentional aging, and aggression due to hardware Trojan (A2) is addressed with proper detection and mitigation mechanisms. The secure and reliable EHS is designed in CMOS 90nm technology. The resulting output is in the range of 3 V to 3.55 V with an input 1 V to 1.5 V. The proposed EHS is consuming power under the micro-watt range that fulfills the ultra-low-power requirements of IoT smart nodes. In acquiring new skill set, a mixed-mode approach is adopted in designing the energy harvesting system that uses Verilog and Verilog-A to model the EHS. The modeled design has been implemented as a SoC for fabrication.