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 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.

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.

Ecotourism activities are attracting more people each day, including national forest parks. Unfortunately, the number of incidents involving visitors to natural parks grows at the same pace. Among the most prevalent risks inside forests are getting lost and the occurrence of natural disasters. In this work, we propose a system for monitoring and assisting visitors of forest parks, based on a low power wide range wireless network, LoRa. The proposed visitor assisting system is composed of mobile terminals that communicate between them and with fixed infrastructure, using a protocol designed for exchanging visitor locations data. The infrastructure consists of wireless gateways distributed on the trails, the totems. User terminals, the mobile nodes, work collaboratively through a Delay and Disruption Tolerant Network (DTN), to cope with the possibility that the gateway infrastructure does not cover the whole trail. In addition to improvements and gains for minimizing risks, the proposal also brings contributions to the preservation of the environment, raising awareness of the influence of human presence in the natural environment and to the development of environmental education actions.