José Geraldo Ribeiro Júnior

Vehicular communications based on IEEE,802.11p promise to improve traffic efficiency and safety in the near future. Embedded with 802.11p-compliant devices, the cooperation among connected vehicles will provide a shift in the way transportation systems operate. Nevertheless, before widespread adoption, extensive performance evaluation of the standard is in need. Due to the high cost and reasonably low availability of commercial devices, most work on VANETs is still performed using simulations. To investigate the equivalence between real experiments and simulations involving 802.11p, this article evaluates the behavior obtained by periodic beacon messages, the basis of safety applications in VANETs. Using commercial OBUs and RSUs, the results are compared with those obtained with NS-3/PhySim and Veins/MiXiM simulators. In V2I and V2V communication scenarios, three key metrics are evaluated: the maximum communication range, packet delivery rate, and packet inter-reception time. The influence of different modulations supported by 802.11p and varying vehicle speeds are also analyzed.

The high cost of IEEE 802.11p-compliant devices and the lack of a widely adopted standard motivate the search for alternative methods for vehicular communication. As a consequence, and due to the ubiquity of smartphones, we see an increasing number of proposals based on Wi-Fi Direct, especially related to the integration of pedestrians in VANETs. Nevertheless, given the complexity of real experimentation, it is difficult to assess the ability of Wi-Fi Direct to offer connectivity in the vehicular environment on a large scale, leading to the evaluation through simulation. In order to verify the ability of a simulation model of reproducing the Wi-Fi Direct behavior, we analyze the performance of a safety application based on the communication range, packet delivery rate, and packet inter-reception time. In V2P scenarios, with and without line of sight, with varying vehicle speed, measurements using smartphones are performed and their results compared with those of OMNeT++ simulator. The results indicate, apart from the simulator’s accuracy, that the connection establishment time hinders the use of Wi-Fi Direct as a replacement to 802.11p. As an outcome of this observation, we evaluate a new transmission method for Wi-Fi Direct based on beacon stuffing, which mitigates the long connection establishment issue.

The constant increase in the number of accidents and traffic jams negatively impacts several areas, including the economy, environment, and health. Since most monitoring systems require high installation and maintenance costs, especially because they depend on a central element, systems based on decentralized infrastructure have emerged as an attractive option. However, these systems cannot guarantee the synchronization between the devices' clocks since there is no centralized element. This paper presents DOCTraMS, a system that monitors and disseminates traffic conditions using a decentralized infrastructure. On-board units and roadside units do not need to be interconnected or connected to a central computer. These elements exchange information to update their tables that describe the traffic conditions of each road segment. To validate DOCTraMS, we have implemented a real IEEE 802.11 b/g prototype at Universidade Federal do Rio de Janeiro Campus. Moreover, we have simulated larger scenarios using NS-3 with traffic data from São Paulo, Brazil. When compared with a GPS, our system accuracy is higher than 90% in all scenarios.

Atualmente, muito se discuti sobre a situação da educação no Brasil e os caminhos que devem ser percorridos para alcançar uma educação de qualidade. Os índices gerados com base em avaliações que medem o nível de proficiência dos alunos não têm desenhado o melhor cenário para o processo de aprendizagem no Brasil. Quando o assunto é matemática, os resultados são caóticos. Porém, vários setores estão se empenhando para construir um painel diferente da educação no Brasil. Nesse contexto, a tecnologia tem sido colocada como uma aliada na tentativa de mudar esse cenário. Partindo dessas observações, o presente trabalho propõe o uso de uma solução tecnológica para dar suporte ao ensino de matemática nos anos iniciais da Educação Básica. A Plataforma foi aplicada a alunos dos anos iniciais do Ensino Fundamental de uma escola da rede pública e observou-se que ela é uma ferramenta eficiente na garantia de um aprendizado contextualizado.

In distributed systems, the lack of synchronism among the devices may result in invalid information and hence incorrect decisions. This paper presents DOCS4V, a distributed system for traffic monitoring that minimises the impact of lack of synchronism by assigning a lifetime to the generated information, which is managed according to the local clock of a device. On-board and Roadside Units share data in order to update their information about the traffic conditions, in addition to propagating alerts about detected obstacles. We performed simulations using IEEE 802.11p in NS-3 to validate DOCS4V. The results reveal that DOCS4V accurately estimates the traffic conditions and efficiently distributes alerts about obstacles, with low network delay, low traffic volume and a high level of successfully delivered frames.

MatematechApp: Aplicativo para Aprendizagem de Matemática nos Anos Iniciais do Ensino Fundamental

Partindo dos desafios propostos pelo atual cenário em que se encontra a educação brasileira e tendo como princípio a importância da tecnologia para o aprendizado, este artigo apresenta a plataforma Matematech, uma solução tecnológica para auxiliar no ensino de conhecimentos básicos de matemática como direção, espaço e operações aritméticas, nos anos iniciais do Ensino Fundamental. A plataforma foi desenvolvida utilizando dispositivos eletrônicos de baixo custo e fácil acesso. Por meio dela, são trabalhados conceitos básicos de matemática através da ação lúdica. A plataforma Matematech foi aplicada a alunos de uma escola da rede pública e observou-se que ela é uma ferramenta eficiente na garantia de um aprendizado contextualizado.

Para muitos estudantes, a complexidade envolvida na utilização do raciocínio lógico cria uma barreira para a construção do conhecimento, principalmente pela dificuldade em visualizar o resultado. Isso é evidente no ensino da lógica, necessária para a criação de algoritmos. Este trabalho tem como objetivo apresentar uma ferramenta para auxiliar o aluno na construção de uma lógica de raciocínio e na visualização da execução desta, de forma simples e clara. A ferramenta é composta por um aplicativo e um hardware responsável por simular e por executar a sequência definida no aplicativo. A ferramenta desenvolvida foi avaliada por alunos que cursam as disciplinas iniciais relacionadas à programação de algoritmos.

Traffic monitoring and control are becoming more and more important as the number of vehicles and traffic jams grow. Nevertheless, these tasks are still predominantly performed by visual means using strategically placed video cameras. For more effectiveness, proposals to improve traffic monitoring and control should consider automated systems. In this paper, we propose the Collaborative and Opportunistic Traffic Monitoring System (COTraMS), which is a system that monitors traffic using available IEEE 802.11 networks. COTraMS is collaborative because user participation is essential in defining the vehicle movement and opportunistic because it uses existing information. To evaluate the performance of COTraMS, a prototype is implemented using an IEEE 802.11 b/g network. Measurements from a real public wireless network in Rio de Janeiro, Brazil, demonstrate the possibility of obtaining traffic conditions with our proposed monitoring system. In addition, we analyze COTraMS via simulation to evaluate its performance in scenarios with a larger number of vehicles. The comparison of the obtained results with data obtained from Global Positioning System shows high accuracy in detecting both the position of the vehicle and the estimation of the road condition, using a simple architecture and a small amount of network bandwidth.

Current proposals of automated traffic monitoring systems for highways require high investment in terms of installation and maintenance, especially because these systems rely on a central element which is responsible for inferring and disseminating the traffic conditions. This paper presents DTraMS (Decentralized Traffic Monitoring System), a system that monitors and disseminates traffic conditions using a decentralized infrastructure. On board units and road side units do not necessarily need to be interconnected, nor connected to a central computer. These elements exchange information to update their tables that describe the traffic conditions of each route section. Vehicles serve as data mules that disseminate the information, whereas road side units store and combine the information received from them. To validate DTraMS, a prototype was implemented using IEEE 802.11b/g and experiments were performed on the campus of Federal University of Rio de Janeiro. The comparison of the results obtained with DTraMS and data obtained with a GPS shows that DTraMS is accurate in detecting both the position of the vehicle and on estimating the road condition.