This article discusses the basics of passive RFID technologies, with an emphasis on tags, for general readers and entrylevel practitioners. Following a brief history of RFID, it describes the types of tags and their operation, and regulations and frequency ranges. It then presents representative applications and describes the major technical hurdles still to be overcome before the adoption of RFID can be widespread, and offers a vision of the technology's future.
A two-stage power conditioning circuit consisting of an AC-DC converter followed by a DC-DC converter is proposed for a vibration-based energy harvesting system. The power conditioning circuit intends to maximize the amount of power extracted from a piezoelectric energy harvester by matching the source impedance with the circuit by adaptively adjusting the duty cycle. An equivalent electrical circuit representation derived from a distributed-parameter piezoelectric energy harvester model is adapted to enable the impedance matching method proposed here. For a given piezoelectric energy harvester, there is a theoretical maximum power output that is determined by the mechanical damping, base acceleration, and the effective mass of the harvester structure under base excitation. Experimental results are given to validate the effectiveness of the proposed resistive impedance matching circuit around the first resonance frequency of a cantilevered piezoelectric energy harvester.
Piezoelectric microelectromechanical systems (PiezoMEMS) are attractive for developing next generation self-powered microsystems. PiezoMEMS promises to eliminate the costly assembly for microsensors/microsystems and provide various mechanisms for recharging the batteries, thereby, moving us closer towards batteryless wireless sensors systems and networks. In order to achieve practical implementation of this technology, a fully assembled energy harvester on the order of a quarter size dollar coin (diameter=24.26 mm, thickness=1.75 mm) should be able to generate about 100 μW continuous power from low frequency ambient vibrations (below 100 Hz). This paper reviews the state-of-the-art in microscale piezoelectric energy harvesting, summarizing key metrics such as power density and bandwidth of reported structures at low frequency input. This paper also describes the recent advancements in piezoelectric materials and resonator structures. Epitaxial growth and grain texturing of piezoelectric materials is being developed to achieve much higher energy conversion efficiency. For embedded medical systems, lead-free piezoelectric thin films are being developed and MEMS processes for these new classes of materials are being investigated. Non-linear resonating beams for wide bandwidth resonance are also reviewed as they would enable wide bandwidth and low frequency operation of energy harvesters. Particle/granule spray deposition techniques such as aerosol-deposition (AD) and granule spray in vacuum (GSV) are being matured to realize the meso-scale structures in a rapid manner. Another important element of an energy harvester is a power management circuit, which should maximize the net energy harvested. Towards this objective, it is essential for the power management circuit of a small-scale energy harvester to dissipate minimal power, and thus it requires special circuit design techniques and a simple maximum power point tracking scheme. Overall, the progress made by the research and industrial community has brought the energy harvesting technology closer to the practical applications in near future.
A Denial of Service (DoS) attack is an incident in which the user is deprived of the services of a resource he is expected to have. With the increasing reliance on mobile devices like laptops and palmtops, a new type of DoS attack is possible that attacks the batteries of these devices, called "sleep deprivation attacks". The goal of sleep deprivation attacks is to rapidly drain the battery of the mobile devices, rendering the device inoperable long before the expected battery lifetime, thus denying the service the user expects from the mobile device. The purpose of this research is to investigate these types of attacks so that proper defense mechanisms can be put in place before the attacks become a more sophisticated and potent force. This research presents three different possible methods that can be adopted by an attacker to drain the battery of a device i.e. malignant attacks, benign attacks and network service request attacks. These attacks are implemented on a variety of mobile computing platforms like palmtops and a laptop and the corresponding results are presented. Finally, a mathematical model is presented that estimates the battery life of a device based on its power consumption in various power management states and expected usage. This model can also be used to predict the impact of a DoS attack on the battery life of the device under attack.
Mobile computers are subject to a unique form of denial of service attack known as a battery exhaustion attack, in which an attacker attempts to rapidly drain the battery of the device. In this paper we present our first steps in the design of an intrusion detection system for these attacks, a system that takes into account the performance, energy, and memory constraints of mobile computing devices. This intrusion detection system uses several parameters, such as CPU load and disk accesses, to estimate the power consumption using a linear regression model, allowing us to find the energy used on a per process basis, and thus identifying processes that are potentially battery exhaustion attacks.
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