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Publicações

Publicações por Francisco Vasques

2016

Timing Analysis of Hybrid FlexRay, CAN-FD and CAN Vehicular Networks

Autores
Lange, R; Bonatto, AC; Vasques, F; de Oliveira, RS;

Publicação
PROCEEDINGS OF THE IECON 2016 - 42ND ANNUAL CONFERENCE OF THE IEEE INDUSTRIAL ELECTRONICS SOCIETY

Abstract
Till nowadays, the Controller Area Network (CAN) has been a de facto standard for communication in automotive applications. To meet the requirements of new high-end vehicular systems, new communication protocols such as the FlexRay Communication System and the CAN with Flexible Data-rate (CAN-FD) has been developed. In the near future, it is expected the coexistence of those protocols in the same vehicle, with electronic control units (ECUs) connected to different network buses exchanging information through gateways. In this paper we investigate the following problem: "how to schedule the communication in a vehicular system, considering that a message is transmitted through a network that is composed of CAN-FD, FlexRay and CAN segments interconnected by gateways." We propose a method for the schedulability analysis of such systems, focusing on the case where a message is generated in a ECU connected to a CAN-FD segment is used by an ECU connected to a CAN bus.

2015

Multimedia transmission in wireless sensor networks

Autores
Costa, DG; Guedes, LA; Vasques, F; Portugal, P;

Publicação
Emerging Research on Networked Multimedia Communication Systems

Abstract
Wireless sensor networks are an emerging technology that can provide valuable information for a large series of monitoring and control applications. Comprising many monitoring scenarios with different particularities, as industrial management, weather forecasting, home automation, traffic management and rescue operations, just to cite a few, wireless sensor networks bring many possibilities for innovative applications that cannot be addressed by conventional wireless network technologies. When sensors are equipped with cameras or microphones, multimedia data can be retrieved from the monitored field, enriching the perception of the target area. However, the constrained nature of wireless sensor networks imposes many challenges to multimedia transmission, fostering development of optimized protocols. In this chapter, we present the state of the art of multimedia transmission in wireless sensor networks, covering topics as routing, error control, congestion avoidance, real-time delivery, compression and QoS, potentially supporting in the development of wireless multimedia sensor networks.

2016

Outlier Detection Using k-means Clustering and Lightweight Methods for Wireless Sensor Networks

Autores
Andrade, ATC; Montez, C; Moraes, R; Pinto, AR; Vasques, F; da Silva, GL;

Publicação
PROCEEDINGS OF THE IECON 2016 - 42ND ANNUAL CONFERENCE OF THE IEEE INDUSTRIAL ELECTRONICS SOCIETY

Abstract
Wireless Sensor Networks (WSNs) are susceptible to faults both in sensors and in communication. Information fusion techniques allow to extract precise information from a large amount of data. Detection, identification and treatment of outlier, in these techniques, is a key point. Outlier detection in WSNs is a challenge due to the low capacity of the nodes and low bandwidth of the network. This paper proposes a methodology that applies the clustering and lightweight statistics techniques for detection of outliers in WSNs. The assessment of the methodology involves a case study with temperature sensors in WSN nodes. The results show that this methodology is able to provide precise information, even in the presence of outliers.

2013

Energy Consumption and Spatial Diversity Trade-off in Autonomic Wireless Sensor Networks: The (m, k)-Gur Game Approach

Autores
Semprebom, T; Pinto, AR; Montez, C; Vasques, F;

Publicação
2013 11TH IEEE INTERNATIONAL CONFERENCE ON INDUSTRIAL INFORMATICS (INDIN)

Abstract
In some Wireless Sensor Network (WSN) applications, it may be necessary to keep a large number of nodes sensing and transmitting data to a base station in order to have unbiased measurement values. Therefore, in addition to the traditional energy consumption issues, the spatial diversity of the monitored area is another relevant metric to evaluate the performance of a WSN. Nevertheless there is a clear trade-off between these two parameters, as keeping the sensors active all the time will deplete the nodes batteries and therefore will shorten the network lifetime. Fortunately, for the case of some applications it is possible to specify as a Quality of Service (QoS) parameter the number of periodically expected messages in the base station. Therefore, it will be possible to balance QoS against energy consumption. This paper proposes an approach called (m, k)-Gur Game that aims a trade-off between the expected QoS and the spatial coverage diversity. Simulation results show the effectiveness of the proposed approach.

2016

An Allocation Scheme for IEEE 802.15.4-ZigBee Cluster-tree Networks

Autores
Leao, E; Vasques, F; Portugal, P; Moraes, R; Montez, C;

Publicação
PROCEEDINGS OF THE IECON 2016 - 42ND ANNUAL CONFERENCE OF THE IEEE INDUSTRIAL ELECTRONICS SOCIETY

Abstract
The IEEE 802.15.4/ZigBee standards support the implementation of cluster-tree networks, which are a suitable topology to deploy wide-scale networks. In this type of topology, an important issue is the configuration of the superframe duration that is allocated to each of the network clusters. In this paper, we propose an allocation scheme for setting up these superframe duration values. The proposed scheme allocates adequate duration values for each cluster coordinator, based on the message load originated from its child nodes (including child coordinators and its descendants). The target of the proposed allocation scheme is to improve the network throughput and to reduce network congestion and dropped messages. Its main advantages are: 1) to have a balanced allocation of network resources to the different clusters; 2) the message generation at the application layer does not need to be synchronised with the beacon arrival; and 3) the message periods do not need to be multiple of the beacon interval.

2017

Alternative Path Communication in Wide-Scale Cluster-Tree Wireless Sensor Networks Using Inactive Periods

Autores
Leao, E; Montez, C; Moraes, R; Portugal, P; Vasques, F;

Publicação
SENSORS

Abstract
The IEEE 802.15.4/ZigBee cluster-tree topology is a suitable technology to deploy wide-scale Wireless Sensor Networks (WSNs). These networks are usually designed to support convergecast traffic, where all communication paths go through the PAN (Personal Area Network) coordinator. Nevertheless, peer-to-peer communication relationships may be also required for different types of WSN applications. That is the typical case of sensor and actuator networks, where local control loops must be closed using a reduced number of communication hops. The use of communication schemes optimised just for the support of convergecast traffic may result in higher network congestion and in a potentially higher number of communication hops. Within this context, this paper proposes an Alternative-Route Definition (ARounD) communication scheme for WSNs. The underlying idea of ARounD is to setup alternative communication paths between specific source and destination nodes, avoiding congested cluster-tree paths. These alternative paths consider shorter inter-cluster paths, using a set of intermediate nodes to relay messages during their inactive periods in the cluster-tree network. Simulation results show that the ARounD communication scheme can significantly decrease the end-to-end communication delay, when compared to the use of standard cluster-tree communication schemes. Moreover, the ARounD communication scheme is able to reduce the network congestion around the PAN coordinator, enabling the reduction of the number of message drops due to queue overflows in the cluster-tree network.

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