Autonomous Energy Management system achieving piezoelectric energy harvesting in Wireless Sensors

International audienceWireless Sensor Networks (WSNs) are extensively used in monitoring applications such as humidity and temperature sensing in smart buildings, industrial automation, and predicting crop health. Sensor nodes are deployed in remote places to sense the data information from the environment and to transmit the sensing data to the Base Station (BS). When a sensor is drained of energy, it can no longer achieve its role without a substituted source of energy. However, limited energy in a sensor's battery prevents the long-term process in such applications. In addition, replacing the sensors' batteries and redeploying the sensors is very expensive in terms of time and budget. To overcome the energy limitation without changing the size of sensors, researchers have proposed the use of energy harvesting to reload the rechargeable battery by power. Therefore, efficient power management is required to increase the benefits of having additional environmental energy. This paper presents a new self-management of energy based on Proportional Integral Derivative controller (PID) to tune the energy harvesting and Microprocessor Controller Unit (MCU) to control the sensor modes

GRAPMAN: Gradual Power Manager for Consistent Throughput of Energy Harvesting Wireless Sensor Nodes

International audienceIn this work, Wireless Sensor Network (WSN) applications that require long-term sustainability are considered. Energy harvesting forms a promising technology to address this challenge, by allowing each node to be entirely powered by energy harvested from its environment. To be sustainable, each node must dynamically adapt its Quality of Service (QoS), regarding the harvested energy using a power management strategy. This strategy is implemented on each node by the Power Manager (PM). In this paper, GRAPMAN (GRAdual Power MANager) is proposed, a novel PM for Energy-Harvesting WSN (EH-WSN) powered by pseudo-periodic energy sources. Unlike most state of the art PMs, GRAPMAN aims to achieve high average throughput while maintaining consistent QoS, i.e. with low fluctuations with respect to time, by looking for the highest throughput that can be supplied by the node over a finite time horizon while remaining sustainable. We show through extensive trace-driven network simulations that GRAPMAN outperforms state of the art PMs in both average throughput and throughput consistency

Efficiency metrics computing in combined sensor networks

This paper discusses the computer-aided design of combined networks for offices and building automation systems based on diverse wired and wireless standards. The design requirements for these networks are often contradictive and have to consider performance, energy and cost efficiency together. For usual office communication, quality of service is more important. In the wireless sensor networks, the energy efficiency is a critical requirement to ensure their long life, to reduce maintenance costs and to increase reliability. The network optimization problem has been solved under considering of overall-costs as objective and quality of service including throughput, delay, packet losses etc. with energy efficiency as required constraints. This can be achieved by a combination of different planning methods like placement of wired and wireless nodes, tracing of cabling systems, energy-efficient sensor management and event-based sampling. A successful application of these methods requires a combined harmonized design at different levels of the networks. This paper aims to demonstrate how these methods are realized in the network planning. These tools provide optimized wired and wireless topologies under considering of costs, distances, transmitted power, frequencies, propagation environments and obstacles given in computer-aided design compatible formats

Variable Data Collection Rate System for a Wildlife Behavior Monitor

Behavior monitors typically collect data, and consequently spend energy, at fixed intervals. For devices that utilize energy harvesting, a fixed data collection interval may result in inefficient battery usage due to variability in available solar radiation. Work was performed for a system capable of adjusting a data collection rate, proportional to changes in battery charge, such that data obtained was maximized without sacrificing battery energy sustainability. Energy consumption, of an actual behavior monitor, was modeled to aid in design and evaluation of a changeable data collection rate system. Model validation was performed by comparing simulated to empirical data for battery charge over time. Proportional Integral Derivative (PID) control was used that changed the rate at which data was collected such that error was minimized between battery State Of Charge (SOC) and a reference point. Gain scheduling was incorporated as a mechanism to resist change in data collection rate caused by fluctuation in available SOC. Gain parameters for a discrete, time domain, PID controller were tuned using a manual, trial and error method. Results of tuning showed improved performance with the absence of Integral control. The system was evaluated by performing simulations for change in available solar energy. Results showed that data collection adjusted to changes in available energy and as a consequence, SOC remained within +/-5% of a reference point

Integrating secure mobile P2P systems and Wireless Sensor Networks

Aquesta tesi tracta de les diferents limitacions trobades a WSN per a habilitar-ne el desplegament en nous escenaris i facilitar la difusió de la informació obtinguda. A un nivell baix, ens centrem en el consum d'energia, mentre que, a un nivell més alt, ens focalitzem en la difusió i la seguretat de la informació. Reduïm el consum d'una mote individual en xarxes amb patrons de trànsit dinàmic mitjançant la definició d'una funció de planificació basada en el conegut controlador PID i allarguem la vida d'una WSN globalment distribuint equitativament el consum energètic de totes les motes, disminuint el nombre d'intervencions necessàries per a canviar bateries i el cost associat. Per tal d'afavorir la difusió de la informació provinent d'una WSN, hem proposat jxSensor, una capa d'integració entre les WSN i el conegut sistema P2P JXTA. Com que tractem informació sensible, hem proposat una capa d'anonimat a JXTA i un mecanisme d'autenticació lleuger per a la seva versió mòbil.Esta tesis trata las diferentes limitaciones encontradas en WSN para habilitar su despliegue en nuevos escenarios, así como facilitar la diseminación de la información obtenida. A bajo nivel, nos centramos en el consumo de energía, mientras que, a un nivel más alto, nos focalizamos en la diseminación y seguridad de la información. Reducimos el consumo de una mota individual en redes con patrones de tráfico dinámico mediante la definición de una función de planificación basada en el conocido controlador PID y alargamos la vida de una WSN globalmente distribuyendo equitativamente el consumo energético de todas las motas, disminuyendo el número de intervenciones requeridas para cambiar baterías y su coste asociado. Para favorecer la diseminación de la información procedente de una WSN hemos propuesto jxSensor, una capa de integración entre las WSN y el conocido sistema P2P JXTA. Como estamos tratando con información sensible, hemos propuesto una capa de anonimato en JXTA y un mecanismo de autenticación ligero para su versión móvil.This thesis addresses different limitations found in WSNs in order to enable their deployment in new scenarios as well as to make it easier to disseminate the gathered information. At a lower level, we concentrate on energy consumption while, at a higher level, we focus on the dissemination and security of information. The consumption of an individual mote in networks with dynamic traffic patterns is reduced by defining a scheduling function based on the well-known PID controller. Additionally, the life of a WSN is extended by equally distributing the consumption of all the motes, which reduces the number of interventions required to replace batteries as well as the associated cost. To help the dissemination of information coming from a WSN we have proposed jxSensor, which is an integration layer between WSNs and the well-known JXTA P2P system. As we are dealing with sensitive information, we have proposed an anonymity layer in JXTA and a light authentication method in its mobile version