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Publications

2018

An Advanced Battery Model for WSN Simulation in Environments With Temperature Variations

Authors
Rodrigues, L; Leao, E; Montez, C; Moraes, R; Portugal, P; Vasques, F;

Publication
IEEE SENSORS JOURNAL

Abstract
Wireless sensor networks (WSNs) can be used to support monitoring activities in a wide range of applications and communication environments. Its usage in extreme conditions, in what concerns pressure, temperature, and humidity, must be carefully assessed before the network deployment. In particular, the temperature variations have a direct impact upon the behavior of WSNs through the batteries of sensor nodes. These electrochemical devices are highly susceptible to temperature variations, which modifies the offered effective charge capacity. In this context, it is difficult to estimate the behavior of batteries over time, impairing the extraction of relevant information for energy-aware approaches. Such information, particularly battery state of charge, voltage, and lifetime, is often used by WSN simulators to predict the communication behavior in different scenarios. Nevertheless, WSN simulators generally use simplistic battery models, causing significant deviations in simulation results when compared with actualWSN deployments. This paper describes the implementation of the Temperature-Dependent Kinetic Battery Model (T-KiBaM) in the Castalia simulator, which enables a considerable improvement of the accuracy of simulations in communication environments with different temperature conditions. An experimental assessment has been performed with temperature variations over time to validate the usage of the T-KiBaM battery model. The experimental results indicate that the T-KiBaM model is quite accurate when estimating battery behavior under both different temperature set points and different temperature variations.

2018

Automated methodology for dependability evaluation of wireless visual sensor networks

Authors
Jesus, TC; Portugal, P; Vasques, F; Costa, DG;

Publication
Sensors (Switzerland)

Abstract
Wireless sensor networks have been considered as an effective solution to a wide range of applications due to their prominent characteristics concerning information retrieving and distributed processing. When visual information can be also retrieved by sensor nodes, applications acquire a more comprehensive perception of monitored environments, fostering the creation of wireless visual sensor networks. As such networks are being more often considered for critical monitoring and control applications, usually related to catastrophic situation prevention, security enhancement and crises management, fault tolerance becomes a major expected service for visual sensor networks. A way to address this issue is to evaluate the system dependability through quantitative attributes (e.g., reliability and availability), which require a proper modeling strategy to describe the system behavior. That way, in this paper, we propose a methodology to model and evaluate the dependability of wireless visual sensor networks using Fault Tree Analysis and Markov Chains. The proposed modeling strategy considers hardware, battery, link and coverage failures, besides considering routing protocols on the network communication behavior. The methodology is automated by a framework developed and integrated with the SHARPE (Symbolic Hierarchical Automated Reliability and Performance Evaluator) tool. The achieved results show that this methodology is useful to compare different network implementations and the corresponding dependability, enabling the uncovering of potentially weak points in the network behavior. © 2018 by the authors. Licensee MDPI, Basel, Switzerland.

2018

A Hybrid Beacon Scheduling Scheme to Allow the Periodic Reconfiguration of Large-scale Cluster-tree WSNs

Authors
Leao, E; Vasconcelos, V; Portugal, P; Montez, C; Moraes, R;

Publication
Proceedings - IEEE 16th International Conference on Industrial Informatics, INDIN 2018

Abstract
The use of Wireless Sensor Network (WSN) based technologies is an attractive solution for large-scale sensing applications (wide area deployment), such as environmental monitoring, precision agriculture and industrial automation. IEEE 802.15.4/ZigBee standards are the most used communication protocols for WSN technologies, where the clustertree topology is pointed out as a suitable topology to support the implementation of large-scale WSNs. These networks are usually scheduled to prioritise convergecast (upstream) traffic generated from sensor nodes toward the sink node. However, this scheduling pattern results in higher delays for control messages (downstream traffic). Within this context, this paper proposes a Hybrid Beacon Scheduling (Fast-HyBeS) scheme to enable the periodic reconfiguration of cluster-tree WSNs. The underlying idea is to periodically schedule a downstream opportunity window, to allow a faster dissemination of control messages. This opportunity window follows a top-down scheduling approach that prioritises the downstream traffic. Simulation results show that the use of Fast-HyBeS can significantly decrease the end-to-end communication delay for control messages, when compared to the use of static convergecast scheduling schemes. Moreover, the simulation results also highlight that the Fast-HyBeS has a negligible impact upon end-to-end communication delays of the monitoring traffic. © 2018 IEEE.

2018

Multiple Mobile Sinks in Event-based Wireless Sensor Networks Exploiting Traffic Conditions in Smart City Applications

Authors
Oliveira, ES; Peixoto, JPJ; Costa, DG; Portugal, P;

Publication
Proceedings - IEEE 16th International Conference on Industrial Informatics, INDIN 2018

Abstract
Modern cities are subject to a lot of periodic or unexpected critical events, which may have different monitoring and control requirements according to the expected impacts on people safety and urban mobility. When multiple monitoring and automation systems are deployed, adaptive wireless sensor networks may adjust sensing and transmission configurations according to the detected events, optimizing the network overall operation. In this context, mobile sinks come as an effective way to enhance monitoring performance in smart city environments. However, practical issues related to the available roads and traffic load should be considered, allowing the computation of the best final positions and movement paths for each sink. Therefore, this paper proposes algorithms to compute dynamic sinks movement in reactive wireless sensor networks, supporting efficient adaptation to event-based monitoring in smart cities. © 2018 IEEE.

2018

On the Computing of Area Coverage by Visual Sensor Networks: Assessing Performance of Approximate and Precise Algorithms

Authors
Jesus, TC; Costa, DG; Portugal, P;

Publication
Proceedings - IEEE 16th International Conference on Industrial Informatics, INDIN 2018

Abstract
Area coverage is an inherent and important topic when dealing with wireless visual sensor networks, since it may be desired when addressing availability and fault tolerance in critical applications. This problem arises because more than one visual sensor may cover the same area, generating overlapped regions that can be exploited for different kinds of optimization and quality enhancement approaches. Actually, some methods to compute the resulted covered area by a set of sensors have been proposed, and they are initial steps to compute availability metrics that are necessary for many monitoring scenarios. Particularly, approximate approaches are promising when computing area coverage, potentially achieving good results, although such methods lack proper evaluation and analysis about complexity, performance and precision. In this context, we perform an evaluation of a recent algorithm based on approximation for area coverage computing, comparing it with a precise algorithm developed in this work for this purpose. Doing so, it is desired to assess performance and accuracy of both algorithms, indicating the most appropriate approach when addressing availability in visual sensor networks. © 2018 IEEE.

Supervised
thesis

2017

Sistema de monitorização de consumo de água utilizando tecnologia Sigfox

Author
Rui Miguel Ribeiro Barbosa

Institution
UP-FEUP

2017

Sistema base para monitorização de parâmetros de máquinas e processos produtivos.

Author
Rui Daniel do Amaral Alves

Institution
UP-FEUP

2016

DySMCAr: Dynamic Star-Mesh Communication Architecture for Manufacturing Wireless Sensor Networks with IEEE 802.15.4e LLDN mode

Author
Benedito Rodrigues Bitencourt Júnior

Institution
UP-FEUP

2016

A Framework to Support Dependability Evaluation pf WSNs from AADL Models

Author
Mara da Silva Benedito Martins

Institution
UP-FEUP

2016

Improving Source-to-Destination Communication Schemes in Wide-Scale Cluster-Tree Wireless Sensor Networks

Author
Erico Meneses Leão

Institution
UP-FEUP