Active Learning of Gaussian Processes for Spatial Functions in Mobile Sensor Networks

This paper proposes a spatial function modeling approach using mobile sensor networks, which potentially can be used for environmental surveillance applications. The mobile sensor nodes are able to sample the point observations of an 2D spatial function. On the one hand, they will use the observations to generate a predictive model of the spatial function. On the other hand, they will make collective motion decisions to move into the regions where high uncertainties of the predictive model exist. In the end, an accurate predictive model is obtained in the sensor network and all the mobile sensor nodes are distributed in the environment with an optimized pattern. Gaussian process regression is selected as the modeling technique in the proposed approach. The hyperparameters of Gaussian process model are learned online to improve the accuracy of the predictive model. The collective motion control of mobile sensor nodes is based on a locational optimization algorithm, which utilizes an information entropy of the predicted Gaussian process to explore the environment and reduce the uncertainty of predictive model. Simulation results are provided to show the performance of the proposed approach. © 2011 IFAC

Towards Augmenting Federated Wireless Sensor Networks

AbstractEnvironmental Monitoring (EM) has witnessed significant improvements in recent years due to the great utility of Wireless Sensor Networks (WSNs). Nevertheless, due to harsh operational conditions in such applications, WSNs often suffer large scale damage in which nodes fail concurrently and the network gets partitioned into disjoint sectors. Thus, reestablishing connectivity between the sectors, via their remaining functional nodes, is of utmost importance in EM; especially in forestry. In this regard, considerable work has been proposed in the literature tackling this problem by deploying Relay Nodes (RNs) aimed at re-establishing connectivity. Although finding the minimum relay count and positions is NP-Hard, efficient heuristic approaches have been anticipated. However, the majority of these approaches ignore the surrounding environment characteristics and the infinite 3-Dimensional (3-D) search space which significantly degrades network performance in practice. Therefore, we propose a 3-D grid-based deployment for relay nodes in which the relays are efficiently placed on grid vertices. We present a novel approach, named FADI, based on a minimum spanning tree construction to re-connect the disjointed WSN sectors. The performance of the proposed approach is validated and assessed through extensive simulations, and comparisons with two main stream approaches are presented. Our protocol outperforms the related work in terms of the average relay node count and distribution, the scalability of the federated WSNs in large scale applications, and the robustness of the topologies formed

Application of the Internet of Things through a Network of Wireless Sensors in a Coffee Crop for Monitoring and Control its Environmental Variables

En este artículo se presenta la aplicación del Internet de las cosas (IoT), como herramienta tecnológica para el desarrollo de una red inalámbrica de sensores, con el objetivo de monitorear y controlar una serie de variables ambientales que inciden en el cultivo del café y su calidad final. Se procedió al diseño lógico y físico de la red y sus dispositivos, se configuró la red de sensores en un terreno determinado y se procedió a recolectar la información de ciertas variables ambientales, para ser comparadas con una serie de parámetros ya establecidos, que permitirán al caficultor observar el comportamiento de dichas variables a través del tiempo y establecer la generación de alertas o advertencias cuando estas medidas se encuentran por fuera de los rangos establecidos. Una vez desarrollado el estudio se pudo determinar que el manejo del cultivo del café es bastante complejo, debido a la gran cantidad de variedades que se encuentran, el terreno y las variables de tipo ambiental que afectan el proceso de producción y la calidad final del grano. Además, se determinó que el desarrollo e implementación de redes inalámbricas de sensores es posible hoy en día por factores como la reducción de los costos de los dispositivos y el uso de software de código abierto, evitándose valores de licenciamiento adicionales. Finalmente, con base en los parámetros analizados, se pudo establecer que uno de los principales problemas en los cultivos de café es la humedad intensa, que en la práctica puede llegar a afectar el rendimiento de los sensores y sus mediciones.This article presents the application of the Internet of things (IoT), as a technological tool for the development of a wireless sensor network with the aim of monitoring and controlling a series of environmental variables affecting the cultivation of coffee and its final quality. The logical and physical design of the network and its devices was carried out, the sensors network was configured in a given field and the information of certain environmental variables was collected to be compared with a series of parameters already established. This procedure will allow the coffee growers to observe the behavior of these variables over time and set the generation of alerts or warnings when these measures are outside the established ranges. The study determined that the management of coffee cultivation is quite complex due to the large number of varieties found, the terrain and environmental variables affecting the production process and the final quality of the grain. It was also determined that the development and implementation of wireless sensor networks is possible today due to factors such as the reduction of device costs and the use of open source software, avoiding additional licensing values. Finally, based on the parameters analyzed, it was possible to establish that one of the main problems in coffee crops is the intense humidity that, in practice, can affect the performance of the sensors and their measurements

Federated Robust Embedded Systems: Concepts and Challenges

The development within the area of embedded systems (ESs) is moving rapidly, not least due to falling costs of computation and communication equipment. It is believed that increased communication opportunities will lead to the future ESs no longer being parts of isolated products, but rather parts of larger communities or federations of ESs, within which information is exchanged for the benefit of all participants. This vision is asserted by a number of interrelated research topics, such as the internet of things, cyber-physical systems, systems of systems, and multi-agent systems. In this work, the focus is primarily on ESs, with their specific real-time and safety requirements. While the vision of interconnected ESs is quite promising, it also brings great challenges to the development of future systems in an efficient, safe, and reliable way. In this work, a pre-study has been carried out in order to gain a better understanding about common concepts and challenges that naturally arise in federations of ESs. The work was organized around a series of workshops, with contributions from both academic participants and industrial partners with a strong experience in ES development. During the workshops, a portfolio of possible ES federation scenarios was collected, and a number of application examples were discussed more thoroughly on different abstraction levels, starting from screening the nature of interactions on the federation level and proceeding down to the implementation details within each ES. These discussions led to a better understanding of what can be expected in the future federated ESs. In this report, the discussed applications are summarized, together with their characteristics, challenges, and necessary solution elements, providing a ground for the future research within the area of communicating ESs

Coverage Characteristics of Symmetric Topologies for Pervasive Sensor Networks

The success of pervasive computing environments comprising ubiquitous loco-dynamic sensing devices is very dependent upon the coverage characteristics (CCs) of the network topology. These characteristics include blanket coverage, network density, affects on surrounding environments and intra-sensor coverage overlaps. This paper presents a systematic mathematical model to quantitatively investigate the effects of CCs and provides a comparison with other well used topologies e.g. hexagonal, triangular and square grid. The paper uses connectivity, density saturation, conflict regions and effectiveness of the topology as quality parameters in simulation studies for a disaster recovery network in various irregular terrains. Numerical as well as simulation results confirm the improved performance of hexagonal topology (HT) in terms of the above mentioned quality parameters which can be used to tune the network design to ensure the required QoS throughout the life of the network