Fabrício A. Silva

On the design of a self-managed wireless sensor network

During the last decade, there was a great technological advance in the development of smart sensors, low-power processors, and wireless communication protocols that when put together create a wireless sensor network (WSN). Smart, autonomous, and self-aware: that is the ultimate vision for WSNs. The success of this vision depends fundamentally on the self-management solutions. This work deals with this challenge: to provide a self-management solution for a WSN that monitors temperature and evaluates fire risks. We focus on self-organization, self-configuration, self-service, and self-maintenance. In particular, we propose service negotiation policies to demonstrate the self-service concept. The results reveal that the management solution can promote the productivity of network resources and the quality of the provided services.

Simulations and Tests of MCP-BSCCO-2212 Superconducting Fault Current Limiters

Superconducting fault current limiters (SCFCLs) represent a promising solution to the problem of increasing short- circuit currents in the grid. The SCFCL is based on the fast transition from the superconducting state to the normal state, causing a sudden increase in the impedance of the network. In this paper, we simulate the behavior of resistive-type SCFCL modules. The SCFCL modules are based on MCP-BSCCO 2212 coils. The superconductor acts as a nonlinear resistance that varies with the current and the temperature. The behavior of the simulated curves is consistent with the experimental results. Short-circuit currents as high as 37 kApeak were limited to about 10% of their peak values in the first half cycle.

On impact of management in wireless sensors networks

A wireless sensor network aims to collect data and, sometimes, control an environment. This kind of network is composed of hundreds to thousands of devices that have the capability of sensing, processing and wireless communicating, called sensor nodes. The sensor nodes are projected with small dimensions (cm/sup 3/ or mm/sup 3/) and this size limitation ends up restraining the node resources, like energy, processor and transceiver capacity. The task of building and deploying management systems in environments where there will be tens of thousand of network elements with particular features and organization is very complex. This task becomes worse due to the physical restrictions of these unattended sensor nodes. In this paper we have implemented and evaluated some automatic services of configuration and performance management, proposed by a WSN management architecture called MANNA. This architecture is based on the paradigm of self-management, which contains the automatic functions and services of management using a minimum of human interference. This work aims to evaluate different WSN configurations considering an application of continuous data sensing and dissemination, and the effects of the management solution proposed for this network. The built application does temperature and carbon monoxide concentration level monitoring, in an urban area. The results show the cost-benefit relations of the different organizations and demonstrates that management can promote the productivity of the resources and control the quality of the provided services.

Vehicular Networks: A New Challenge for Content-Delivery-Based Applications

A significant number of promising applications for vehicular ad hoc networks (VANETs) are becoming a reality. Most of these applications require a variety of heterogenous content to be delivered to vehicles and to their on-board users. However, the task of content delivery in such dynamic and large-scale networks is easier said than done. In this article, we propose a classification of content delivery solutions applied to VANETs while highlighting their new characteristics and describing their underlying architectural design. First, the two fundamental building blocks that are part of an entire content delivery system are identified: replica allocation and content delivery. The related solutions are then classified according to their architectural definition. Within each category, solutions are described based on the techniques and strategies that have been adopted. As result, we present an in-depth discussion on the architecture, techniques, and strategies adopted by studies in the literature that tackle problems related to vehicular content delivery networks.

Designing mobile content delivery networks for the internet of vehicles

Abstract Content delivery is a key functionality for developing the Internet of Vehicles. In such networks, vehicles act as sensors of the urban mobility by constantly exchanging messages with another vehicles, the cellular network, and also the infrastructure (roadside units). However, the task of delivering content in such dynamic network is far from trivial. In this work, we investigate the development of Content Delivery Networks (CDN) in the context of vehicular networks. Roadside units support the communication by replicating and delivering contents to vehicles within their range of coverage. Initially, we devise a strategy for measuring the performance of the content delivery in vehicular networks. Then, we use the proposed metric for designing a deployment strategy allowing us to identify the better locations for deploying the roadside units in order to properly support the dissemination of a variety of contents, each content requiring specific levels of performance. We compare our deployment strategy to the intuitive strategy of allocating roadside units at the densest locations of the road network. The results demonstrate that our strategy requires less roadside units than the baseline for non-massive deployments in order to achieve similar levels of performance, incurring in less costs when setting up the content-delivery infrastructure.

Improving VANET Simulation with Calibrated Vehicular Mobility Traces

Simulation is the most frequently adopted approach for evaluating protocols and algorithms for Vehicular Ad hoc Networks (VANETs) and Delay-Tolerant Networks (DTNs). Usually, simulation tools use mobility traces to build the network topology based on the existing contacts between mobile nodes. However, quality of the traces, in terms of spatial and temporal granularity of each entry in the logfile, is a key factor that impacts the network topology directly. Therefore, the reliability of the results depends strongly on the accurate representation of the real network topology by the vehicular mobility model. We show that five widely adopted existing real vehicular mobility traces present gaps, leading to fallible outcomes. In this work, we propose a solution to fill those gaps, leading to more fine-grained traces, which lead to more trustworthy simulation results. We propose and evaluate a data-based solution using clustering algorithms to fill the gaps of real-world traces. In addition, we also present the evaluation results that compare the communication graph of the original and the calibrated traces using network metrics. The results reveal that the gaps do indeed induce network topologies differing from reality, decreasing the quality of the evaluation results. To contribute to the research community, we have made the calibrated traces publicly available, so that other researchers may adopt them to improve their evaluation results.

A Tiny and Light-Weight Autonomic Element for Wireless Sensor Networks

Autonomic networks are able to monitor and control themselves without direct human intervention. The smallest unit of an autonomic network is the autonomic element (AE). This work presents the model and evaluation of a specific wireless sensor network (WSNs) AE, called autonomic sensor element (ASE). The ASE has been proposed considering WSNs hardware, software, communication and energy restrictions.

ODCRep: Origin–Destination-Based Content Replication for Vehicular Networks

The evolution of vehicular network applications, from simple alert message exchange to more elaborate and sophisticated systems, boosts the need for content delivery solutions. A useful technique, in this case, is content replication, in which strategically selected vehicles replicate content and help in the delivery process. However, content replication is particularly challenging in vehicular networks, due to their special characteristics, such as highly dynamic topology, diverse density, and large-scale scenarios. Although there has been progress in routing and dissemination solutions for vehicular networks, few studies have concentrated on the content replication problem. To address this issue, we propose an origin-destination-based content replication (ODCRep) solution that focuses on balancing the number of replicas across the application area. Differently from existing solutions, ODCRep relies only on the origin-destination information and uses computationally efficient algorithms. Results from exhaustive simulations show that ODCRep can achieve high coverage, yet can also consume fewer resources than existing solutions.

A novel macroscopic mobility model for vehicular networks

Researchers face a great challenge when evaluating large-scale vehicular ad hoc network solutions. Since it is not feasible to perform real experiments in this case, and there are no large-scale testbeds available, simulation is the most frequently used evaluation technique, which requires a realistic mobility model to provide accurate results. However, building large-scale realistic vehicular mobility models is a difficult task and many important characteristics have been neglected, particularly macroscopic ones. In this work, a realistic vehicular mobility trace is characterized and macroscopic features are inferred. Based on this characterization, we propose and validate a macroscopic mobility model that provides more realistic characteristics to the vehicular network evaluation process. The obtained results contribute to the research community by providing a more realistic macroscopic model that complements many vehicular mobility generators available in the literature.

On the Improvement of Vehicular Macroscopic Mobility Models

Evaluating large scale vehicular networks solutions is a great challenge once real experiments are not feasible yet and there are no large scale testbeds available. Thus, the most used evaluation technique is simulation, which requires a realistic mobility model to provide accurate results. However, building large scale realistic vehicular mobility models is a hard task and many important characteristics have been neglected, like the origin-destination (O-D) macroscopic one. In this work it is proposed a trace-based O-D macroscopic model inferred by the adoption of statistical techniques in order to characterize a validated traffic model. This work contributes to the research community by providing a more realistic O-D macroscopic model, which can be considered a complement for many traffic generators available in literature.