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Publications

Publications by Francisco Vasques

2005

Real-time traffic separation in shared ethernet networks: Simulation analysis of the h-BEB collision resolution algorithm

Authors
Moraes, R; Vasques, F;

Publication
11TH IEEE INTERNATIONAL CONFERENCE ON EMBEDDED AND REAL-TIME COMPUTING SYSTEMS AND APPLICATIONS, PROCEEDINGS

Abstract
In this paper, the enhanced collision resolution algorithm, referred as high priority Binary Exponential Backoff (h-BEB) is analyzed. Such algorithm provides high priority traffic separation, enabling the support of real-time communication in shared Ethernet networks. It allows multiple Ethernet standard devices to coexist in the same network segment with one h-BEB enhanced station, imposing higher priority for the transfer of h-BEB related traffic. The simulation analysis shows that the h-BEB algorithm guarantees values for both the average access delay and the related standard deviation, that are significantly smaller for the h-BEB station than for the BEB stations.

2008

Performance Evaluation of a Compression Algorithm for Wireless Sensor Networks in Monitoring Applications

Authors
Silva, IMD; Guedes, LA; Vasques, F;

Publication
2008 IEEE INTERNATIONAL CONFERENCE ON EMERGING TECHNOLOGIES AND FACTORY AUTOMATION, PROCEEDINGS

Abstract
Wireless sensor network (WSN) is an emerging technology that targets multiple applications in the different environments. Its infrastructure is composed of a large number of sensor nodes with a limited physical capacity and low cost. The energy consumption must be as optimized as possible in order to extend its lifetime. The use of data compression techniques can be an advantage in the WSN context, once these techniques eliminate transmission of redundant information and consequently can be adopted to minimize the consumption of energy in the sensor nodes. WSN for monitoring applications can benefit from this technique as it may maximize the lifetime of batteries. The main motivation of this paper is to investigate the performance of a data compression algorithm for WSN in the context of monitoring applications. To validate the proposal, simulation experiments have been performed using the Network Simulator (NS-2) tool.

2008

Genetic Machine Learning Approach for Data Fusion Applications in Dense Wireless Sensor Networks

Authors
Pinto, AR; Bitencort, B; Dantas, MAR; Montez, CB; Vasques, F;

Publication
2008 IEEE INTERNATIONAL CONFERENCE ON EMERGING TECHNOLOGIES AND FACTORY AUTOMATION, PROCEEDINGS

Abstract
Wireless Sensor Networks (WSN) are being targeted for use in applications like security, resources monitoring and factory automation. However, the reduced available resources raise a lot of technical challenges. Self organization in WSN is a desirable characteristic that can be achieved by means of data fusion techniques when delivering reliable data to users. In this paper it is proposed a genetic machine learning algorithm (GMLA) approach that makes a trade-off between quality of information and communication efficiency. GMLA is based on genetic algorithms and it can adapt itself dynamically to environment modifications. The main target of the proposed approach is to achieve set(organization in a WSN application with data fusion. Simulations demonstrate that the proposed approach can optimize communication efficiency in a dense WSN.

2005

Real-time communication in unconstrained shared ethernet networks: The virtual token-passing approach

Authors
Borges Carreiro, FB; Moraes, R; Fonseca, JA; Vasques, F;

Publication
ETFA 2005: 10TH IEEE INTERNATIONAL CONFERENCE ON EMERGING TECHNOLOGIES AND FACTORY AUTOMATION, VOL 1, PTS 1 AND 2, PROCEEDINGS

Abstract
Traditional shared Ethernet networks have a non-deterministic behaviour, which impairs the support of real-time communication. In this paper, it is proposed a shared Ethernet deterministic architecture, able to interconnect sensors, controllers and actuators at the field level, allowing the coexistence of standard devices with enhanced (real-time). devices. Such solution is based on the control of the medium access right, by means of a virtual token passing procedure among enhanced stations, complemented by an underlying prioritization mechanism. Such underlying mechanism guarantees that, whenever an enhanced (real-time) station is contending for the bus access, it will be able to access the bus prior to any other station. Thus, it enables the traffic separation between standard and enhanced (real-time) stations, being able to guarantee real-time communication in unconstrained traffic environments.

2008

On the Timeliness of Multi-Hop Non-Beaconed ZigBee Broadcast Communications

Authors
Bartolomeu, P; Fonseca, J; Vasques, F;

Publication
2008 IEEE INTERNATIONAL CONFERENCE ON EMERGING TECHNOLOGIES AND FACTORY AUTOMATION, PROCEEDINGS

Abstract
This paper studies the adoption of the ZigBee technology to replace broadcast-based wired communications in automation systems for Health Smart Homes. An analytical study is presented as well as the experimental results validating the derived expressions. Results show that the timeliness of ZigBee broadcast communications, in interference-free environments, can cope with the requirements of home automation applications and those found in building automation.

2002

Transparent environment for replicated Ravenscar applications

Authors
Pinho, LM; Vasques, F;

Publication
RELIABLE SOFTWARE TECHNOLOGIES - ADA-EUROPE 2002

Abstract
This paper proposes an environment intended for the development of fault-tolerant real-time Ada 95 applications conforming to the Ravenscar profile. This environment is based on the transparent replication of application components, and it provides a set of generic task interaction objects, which are used as the basic building blocks of the supported applications. These objects provide the usual task interaction mechanisms used in hard real-time applications, and allow applications to be developed without considering replication and distribution issues.

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