1,721,153 research outputs found
Slotted ALOHA Overlay on LoRaWAN: a Distributed Synchronization Approach
No full textLoRaWAN is one of the most promising standards for IoT applications.
Nevertheless, the high density of end-devices expected for each gateway, the
absence of an effective synchronization scheme between gateway and end-devices,
challenge the scalability of these networks. In this article, we propose to
regulate the communication of LoRaWAN networks using a Slotted-ALOHA (S-ALOHA)
instead of the classic ALOHA approach used by LoRa. The implementation is an
overlay on top of the standard LoRaWAN; thus no modification in pre-existing
LoRaWAN firmware and libraries is necessary. Our method is based on a novel
distributed synchronization service that is suitable for low-cost IoT
end-nodes. S-ALOHA supported by our synchronization service significantly
improves the performance of traditional LoRaWAN networks regarding packet loss
rate and network throughput
NETWIS: A Scalable and Robust Body SensorNetwork For Biomedical Application
No full textWireless wearable sensors have developed rapidly in recent years, primarily driven by e-health, fitness and wellness applications. The technological evolution of low power microprocessors is enabling to process data locally, saving energy and bandwidth and increasing the overall throughput of the wireless network. This paper presents a new general-purpose Inertial Measure Unit that exploits a dual-core architecture. A core offers processing capability, and the other one is a radio interface IEEE 802.15.4. We propose the whole system and a protocol to maximize the throughput, reduce the packet loss and improve the robustness of wireless sensor nodes communication. Experimental results show that our solution offers better data throughput for configurations below 10 nodes compared to widely used commercial wireless sensor nodes. The paper also presents an experimental evaluation of scalability (up to 10 nodes) and power consumption of the proposed solution
Clamp-and-measure forever: A MOSFET-based circuit for energy harvesting and measurement targeted for power meters5th IEEE International Workshop on Advances in Sensors and Interfaces IWASI
No full textSmart metering applications for monitoring the power usage of industrial or household appliances are rapidly increasing. At the same time, constraints such as the ease of installation and a long lifetime have boosted the interest in developing dedicated wireless sensor networks combined with energy harvesting systems and contact-less sensors. In this paper we present a hybrid circuit, tailored for wireless current meters, which performs current measurement and power supply extraction from the same non-invasive, clamp-on current transformer. A power saving MOSFET-based switch system (MSwS) connects the current sensor to the harvesting circuit during the node sleep time and to the measurement circuit when the node is active according to a proper operating duty-cycle. Experimental results show that the energy spent during the active phase can be totally recovered during the sleep time interval making the sensor node capable to self-sustain its operations and to operate without batteries indefinitely
Improving the efficiency of air-flow energy harvesters combining active and passive rectifiers
No full textThe architecture of air-flow energy harvesters generally consists of a first rectifying stage followed by a DC-DC regulator to convert and to store the incoming energy. This paper presents a circuit designed to improve the efficiency of the rectifying stage combining a MOSFET-based active rectifier in parallel with a passive full-wave bridge. Such system exploits the low forward voltage of the Schottky diodes to compensate the drawback of the inefficient passive rectification due to the bulk diodes of the MOSFETs when the power generated by low air-flow speed is not sufficient to activate the control circuitry of the active rectifier. The hybrid rectifier concept was firstly analyzed by SPICE simulations and next validated by means of experiments. Results show a conversion efficiency improvement between 10% and 30%. Moreover an energy harvester equipped with the hybrid rectifier shows an increase of the collected energy from 7% to 11% with respect to a scavenger using the active topology
Exploring Scalable, Distributed Real-Time Anomaly Detection for Bridge Health Monitoring
Full text linkModern real-time Structural Health Monitoring systems can generate a considerable amount of information that must be processed and evaluated for detecting early anomalies and generating prompt warnings and alarms about the civil infrastructure conditions. The current cloud-based solutions cannot scale if the raw data has to be collected from thousands of buildings. This paper presents a full-stack deployment of an efficient and scalable anomaly detection pipeline for SHM systems which does not require sending raw data to the cloud but relies on edge computation. First, we benchmark three algorithmic approaches of anomaly detection, i.e., Principal Component Analysis (PCA), Fully-Connected AutoEncoder (FC-AE), and Convolutional AutoEncoder (C-AE). Then, we deploy them on an edge-sensor, the STM32L4, with limited computing capabilities. Our approach decreases network traffic by ≈ 8·105×, from 780KB/hour to less than 10 Bytes/hour for a single installation and minimize network and cloud resource utilization, enabling the scaling of the monitoring infrastructure. A real-life case study, a highway bridge in Italy, demonstrates that combining near-sensor computation of anomaly detection algorithms, smart pre-processing, and low-power wide-area network protocols (LPWAN) we can greatly reduce data communication and cloud computing costs, while anomaly detection accuracy is not adversely affected
Self-powered wireless energy meterProceedings of the 1st International Workshop on Energy Neutral Sensing Systems - ENSSys '13
No full textWe present the design of a Wireless Electrical Energy Metering node (WEM) for the integration in a wireless sensor network. The node has energy harvesting capability for long lasting monitoring, and measures the power consumption, of residential and industrial appliances, in the range 10W--10kW. Energy harvesting makes the monitoring activity completely energy autonomous by exploiting a single current transformer to scavenge energy from the electromagnetic field of the main and to perform the measure of current consumption of the load
A power-aware multi harvester power unit with hydrogen fuel cell for embedded systems in outdoor applications2013 International Green Computing Conference Proceedings
No full textEnergy availability and long term operation are key challenges for wireless sensor networks and the applications where embedded devices are battery-operated and they should operate unattended for tens of years. For this reason energy harvesting (EH) is becoming very important for powering ubiquitously deployed sensor networks and mobile electronics. In this paper we introduce a Smart Power Unit (SPU) for embedded systems which integrates energy harvesters from the sun and wind with hydrogen fuel cells especially designed for outdoor applications. The power unit can work as a standard battery or providing serial communication to exchange power information to achieve power management.Experimental results show the high efficiency (up to 90%) of the power conversion subsystem and the perpetual work. Deployment in a structural health monitoring in Switzerland demonstrates that perpetual energy sustainability is achievable in real-life conditions
Heterogeneous multi-harvester for wireless sensor networks
No full textThe majority of Wireless Sensor Networks (WSNs) applications requires long-term and unattended operation for each wireless sensor node. Scavenging energy from the surrounding environment has become an established technique to match the power demand of the nodes and to overcome the bottlenecks due to the battery-powered devices. In this demonstration we will show a microcontroller-based architecture which can collect energy from light and air-flow by performing high-efficiency conversion (higher than 80%)and maximum power point tracking algorithms. Experimental results obtained from the deployment in a structural health monitoring system in Switzerland have shown that energy neutrality is achievable in real-life scenarios
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