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Tales Heimfarth
Computer Science Department, Federal University of Lavras, Lavras 37200-000, Brazil.

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Journal article
Published: 20 December 2017 in Sensors
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With the emerging Internet of Things (IoT) technology becoming reality, a number of applications are being proposed. Several of these applications are highly dependent on wireless sensor networks (WSN) to acquire data from the surrounding environment. In order to be really useful for most of applications, the acquired data must be coherent in terms of the time in which they are acquired, which implies that the entire sensor network presents a certain level of time synchronization. Moreover, to efficiently exchange and forward data, many communication protocols used in WSN rely also on time synchronization among the sensor nodes. Observing the importance in complying with this need for time synchronization, this work focuses on the second synchronization problem, proposing, implementing and testing a time synchronization service for low-power WSN using low frequency real-time clocks in each node. To implement this service, three algorithms based on different strategies are proposed: one based on an auto-correction approach, the second based on a prediction mechanism, while the third uses an analytical correction mechanism. Their goal is the same, i.e., to make the clocks of the sensor nodes converge as quickly as possible and then to keep them most similar as possible. This goal comes along with the requirement to keep low energy consumption. Differently from other works in the literature, the proposal here is independent of any specific protocol, i.e., it may be adapted to be used in different protocols. Moreover, it explores the minimum number of synchronization messages by means of a smart clock update strategy, allowing the trade-off between the desired level of synchronization and the associated energy consumption. Experimental results, which includes data acquired from simulations and testbed deployments, provide evidence of the success in meeting this goal, as well as providing means to compare these three approaches considering the best synchronization results and their costs in terms of energy consumption.

ACS Style

Leandro Tavares Bruscato; Tales Heimfarth; Edison Pignaton De Freitas. Enhancing Time Synchronization Support in Wireless Sensor Networks. Sensors 2017, 17, 2956 .

AMA Style

Leandro Tavares Bruscato, Tales Heimfarth, Edison Pignaton De Freitas. Enhancing Time Synchronization Support in Wireless Sensor Networks. Sensors. 2017; 17 (12):2956.

Chicago/Turabian Style

Leandro Tavares Bruscato; Tales Heimfarth; Edison Pignaton De Freitas. 2017. "Enhancing Time Synchronization Support in Wireless Sensor Networks." Sensors 17, no. 12: 2956.

Journal article
Published: 25 September 2013 in Sensors
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This paper presents a bio-inspired networking strategy to support the cooperation between static sensors on the ground and mobile sensors in the air to perform surveillance missions in large areas. The goal of the proposal is to provide low overhead in the communication among sensor nodes, while allocating the mobile sensors to perform sensing activities requested by the static ones. Simulations have shown that the strategy is efficient in maintaining low overhead and achieving the desired coordination.

ACS Style

Edison Pignaton De Freitas; Tales Heimfarth; Alexey Vinel; Flávio Rech Wagner; Carlos Eduardo Pereira; Tony Larsson. Cooperation among Wirelessly Connected Static and Mobile Sensor Nodes for Surveillance Applications. Sensors 2013, 13, 12903 -12928.

AMA Style

Edison Pignaton De Freitas, Tales Heimfarth, Alexey Vinel, Flávio Rech Wagner, Carlos Eduardo Pereira, Tony Larsson. Cooperation among Wirelessly Connected Static and Mobile Sensor Nodes for Surveillance Applications. Sensors. 2013; 13 (10):12903-12928.

Chicago/Turabian Style

Edison Pignaton De Freitas; Tales Heimfarth; Alexey Vinel; Flávio Rech Wagner; Carlos Eduardo Pereira; Tony Larsson. 2013. "Cooperation among Wirelessly Connected Static and Mobile Sensor Nodes for Surveillance Applications." Sensors 13, no. 10: 12903-12928.

Journal article
Published: 31 August 2013 in Ad Hoc Networks
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The use of mobile software agents is a promising approach to implement services and disseminate data over ad hoc networks. This paper presents an analysis of mobile autonomous agents with different levels of intelligence that allow them to make usage of the positioning information with different complexity in a mobile ad hoc network aiming at efficient data dissemination. This information considers the nodes current and future locations, as well as the route used to reach their destinations, depending on the agents’ intelligence. Using this information, the agents decide their movement from node to node during opportunistic connections in order to accomplish their goals related to data dissemination and/or service provisioning. The analysis of this proposal is done in the context of a sensor network application, implemented by sensing services provided by mobile agents, which run on top of an infrastructure-less Vehicular Ad hoc Network (VANET). Simulation results are presented and discussed to support the proposed ideas.

ACS Style

Edison Pignaton de Freitas; Tales Heimfarth; Flavio Rech Wagner; Carlos Eduardo Pereira; Tony Larsson. Exploring geographic context awareness for data dissemination on mobile ad hoc networks. Ad Hoc Networks 2013, 11, 1746 -1764.

AMA Style

Edison Pignaton de Freitas, Tales Heimfarth, Flavio Rech Wagner, Carlos Eduardo Pereira, Tony Larsson. Exploring geographic context awareness for data dissemination on mobile ad hoc networks. Ad Hoc Networks. 2013; 11 (6):1746-1764.

Chicago/Turabian Style

Edison Pignaton de Freitas; Tales Heimfarth; Flavio Rech Wagner; Carlos Eduardo Pereira; Tony Larsson. 2013. "Exploring geographic context awareness for data dissemination on mobile ad hoc networks." Ad Hoc Networks 11, no. 6: 1746-1764.

Journal article
Published: 15 April 2013 in Informatics in Education
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Publisher: Vilnius University Institute of Data Science and Digital Technologies, Journal: Informatics in Education, Title: The Experience of Using the Scrum Process in the Production of Learning Objects for Blended Learning, Authors: Raphael Winckler de BETTIO, Denilson Alves PEREIRA, Ronei Ximenes MARTINS, Tales HEIMFARTH , The technological resources used for pedagogical innovation in the form of distance education have increasingly been incorporated into face-to-face education. This article describes the experience of the Federal University of Lavras - Brazil - with new ways to apply technology in face-to-face undergraduate courses. This paper presents (i) the strategy for the selection of course content, which was premised on the diversification of areas of knowledge and on promoting the permanent incorporation of the resources developed in the teaching-learning process, (ii) the organization of the production process of Learning Objects based on the Scrum method, (iii) the set of best practices, inspired by the management of agile software development, as well as the contextual motivation of its use.

ACS Style

Raphael Winckler De Bettio; Denilson Alves Pereira; Ronei Ximenes Martins; Tales Heimfarth. The Experience of Using the Scrum Process in the Production of Learning Objects for Blended Learning. Informatics in Education 2013, 12, 29 -41.

AMA Style

Raphael Winckler De Bettio, Denilson Alves Pereira, Ronei Ximenes Martins, Tales Heimfarth. The Experience of Using the Scrum Process in the Production of Learning Objects for Blended Learning. Informatics in Education. 2013; 12 (1):29-41.

Chicago/Turabian Style

Raphael Winckler De Bettio; Denilson Alves Pereira; Ronei Ximenes Martins; Tales Heimfarth. 2013. "The Experience of Using the Scrum Process in the Production of Learning Objects for Blended Learning." Informatics in Education 12, no. 1: 29-41.

Proceedings article
Published: 01 January 2011 in Proceedings of the 2011 ACM Symposium on Applied Computing - SAC '11
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ACS Style

Edison Pignaton De Freitas; Tales Heimfarth; Luiz Augusto Guimarães Costa; Armando M. Ferreira; Carlos Eduardo Pereira; Flávio Rech Wagner; Tony Larsson. Analyzing different levels of geographic context awareness in agent ferrying over VANETs. Proceedings of the 2011 ACM Symposium on Applied Computing - SAC '11 2011, 1 .

AMA Style

Edison Pignaton De Freitas, Tales Heimfarth, Luiz Augusto Guimarães Costa, Armando M. Ferreira, Carlos Eduardo Pereira, Flávio Rech Wagner, Tony Larsson. Analyzing different levels of geographic context awareness in agent ferrying over VANETs. Proceedings of the 2011 ACM Symposium on Applied Computing - SAC '11. 2011; ():1.

Chicago/Turabian Style

Edison Pignaton De Freitas; Tales Heimfarth; Luiz Augusto Guimarães Costa; Armando M. Ferreira; Carlos Eduardo Pereira; Flávio Rech Wagner; Tony Larsson. 2011. "Analyzing different levels of geographic context awareness in agent ferrying over VANETs." Proceedings of the 2011 ACM Symposium on Applied Computing - SAC '11 , no. : 1.

Journal article
Published: 10 March 2010 in International Journal of Computers Communications & Control
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Sensor networks are being used to implement different types of sophisticated emerging applications, such as those aimed at supporting ambient intelligence and surveillance systems. This usage is enhanced by employing sensors with different characteristics in terms of sensing, computing and mobility capabilities, working cooperatively in the network. However, the design and deployment of these heterogeneous systems present several issues that have to be handled in order to meet the user expectations. The main problems are related to the nodes‘ interoperability and the overall resource allocation, both inter and intra nodes. The first problem requires a common platform that s the nodes’ heterogeneity and provides a smooth communication, while the second is handled by cooperation mechanisms supported by the platform. Moreover, as the nodes are supposed to be heterogeneous, a customizable platform is required to support both resource rich and poorer nodes. This paper analyses surveillance systems based on a heterogeneous sensor network, which is composed by lowend ground sensor nodes and autonomous aerial robots, i.e. Unmanned Aerial Vehicles (UAVs), carrying different kinds of sensors. The approach proposed in this work tackles the two above mentioned problems by using a customizable hardware platform and a middleware to support interoperability. Experimental results are also provided.

ACS Style

Edison Pignaton De Freitas; Tales Heimfarth; Rodrigo Schmidt Allgayer; Flávio Rech Wagner; Tony Larsson; Carlos Eduardo Pereira; Armando Morado Ferreira. Coordinating Aerial Robots and Unattended Ground Sensors for Intelligent Surveillance Systems. International Journal of Computers Communications & Control 2010, 5, 52 .

AMA Style

Edison Pignaton De Freitas, Tales Heimfarth, Rodrigo Schmidt Allgayer, Flávio Rech Wagner, Tony Larsson, Carlos Eduardo Pereira, Armando Morado Ferreira. Coordinating Aerial Robots and Unattended Ground Sensors for Intelligent Surveillance Systems. International Journal of Computers Communications & Control. 2010; 5 (1):52.

Chicago/Turabian Style

Edison Pignaton De Freitas; Tales Heimfarth; Rodrigo Schmidt Allgayer; Flávio Rech Wagner; Tony Larsson; Carlos Eduardo Pereira; Armando Morado Ferreira. 2010. "Coordinating Aerial Robots and Unattended Ground Sensors for Intelligent Surveillance Systems." International Journal of Computers Communications & Control 5, no. 1: 52.

Journal article
Published: 09 December 2009 in The Computer Journal
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The emerging applications using sensor network technologies constitute a new trend requiring several different devices to work together and partly autonomously. However, the integration and coordination of heterogeneous sensors in these emerging systems is still a challenge, especially when the target application scenario is susceptible to constant changes. The setup and adaptation of these systems are challenging, considering that their nodes are distributed and must respect operational constraints, such as energy consumption. Due to the dynamicity of the scenarios in which they are deployed and the nature of their operations these systems require autonomous decisions that have to be taken without any human operator intervention. This paper presents a reflective middleware that supports heterogeneous sensor networks deployed in dynamic scenarios. This middleware presents specific handling of users’ requirements by representing them as missions that must be accomplished by the network. These missions are then translated to network parameters and activities that are distributed to network nodes by means of the autonomous reasoning that takes into account network nodes’ capabilities and environment conditions. A multi-agent framework is proposed to provide the necessary support for missions’ dissemination and for the required reasoning to allow autonomous behaviour related to mission allocation and network adaptation.

ACS Style

Edison Pignaton de Freitas; Tales Heimfarth; Carlos Eduardo Pereira; Armando Morado Ferreira; Flávio Rech Wagner; Tony Larsson. Multi-Agent Support in a Middleware for Mission-Driven Heterogeneous Sensor Networks. The Computer Journal 2009, 54, 406 -420.

AMA Style

Edison Pignaton de Freitas, Tales Heimfarth, Carlos Eduardo Pereira, Armando Morado Ferreira, Flávio Rech Wagner, Tony Larsson. Multi-Agent Support in a Middleware for Mission-Driven Heterogeneous Sensor Networks. The Computer Journal. 2009; 54 (3):406-420.

Chicago/Turabian Style

Edison Pignaton de Freitas; Tales Heimfarth; Carlos Eduardo Pereira; Armando Morado Ferreira; Flávio Rech Wagner; Tony Larsson. 2009. "Multi-Agent Support in a Middleware for Mission-Driven Heterogeneous Sensor Networks." The Computer Journal 54, no. 3: 406-420.