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One of the main limitations that still keeps Wireless Sensor Networks (WSNs) from being adopted in a large scale is the limited energy supply, i.e. the lifetime of the nodes that constitute the network. The wireless communication between nodes is responsible for most of the energy consumed in WSNs. A promising method to improve the energy efficiency is the usage of a Cooperative Multiple Input Multiple...
Many important signal processing techniques such as Spatial Smoothing, Forward Backward Averaging and Root-MUSIC, rely on antenna arrays with specific and precise structures. Arrays with such ideal structures, such as a centro-hermitian structure, are often hard to build in practice. Array interpolation is used to enable the usage of these techniques with imperfect (not having a centro-hermitian structure)...
It is impossible to enforce exact responses for each sensor involved in an antenna array. Important signal processing techniques such as Estimation of Signal Parameters via Rotational Invariance (ESPRIT), Forward Backward Average (FBA) and Spatial Smoothing (SPS) rely on sensor arrays with Vandermonde or centro-hermitian responses. To achieve such responses array interpolation is often necessary....
Sensor arrays with Vandermonde or centro-hermitian responses cannot always be constructed. However, such array response structure can be achieved by means of a mapping which transforms the real array response to an array response with the desired properties by applying array interpolation algorithms. In this work a low-complexity, multi-sector, signal adaptive array interpolation approach that achieves...
Research advances in materials science improved gradually photovoltaic systems efficiency. However, such systems are limited to work in the presence of sun light, and they also depend on the geographic localization and on the period of the year, usually limited to 6 to 8 hours a day. In order to take maximum advantage of solar panels, it is crucial to use them also in cloudy weather or even at night...
One possible way to define the end of lifetime for a Wireless Sensor Network (WSN) is to set a threshold for the number of disconnections among the sensor nodes so that above this level the WSN becomes unable to provide the quality of services required by the users or even totally loses its ability to provide any service at all. Disconnections isolate sensors or group of sensors which cannot deliver...
Energy consumption in Wireless Sensor Networks (WSNs) is a limiting factor that hinders the application of such networks into solving a broader set of problems. Various ways of saving energy have been proposed, from energy efficient processing to power aware cluster organization. With communication between nodes being responsible for a large part of the energetic demand, energy efficient methods of...
Unmanned aerial vehicles (UAVs) are used in various applications such as civil and military surveillance, law enforcement, and support in natural disasters as well as in hazardous environments. Approaching and landing are necessary steps for all UAVs, indicating that radio altimeters are needed. In this paper, a radio altimeter based on an antenna array is proposed. Our solution allows some improvements...
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