Hugo Conceição

Self-organized traffic control

In this paper we propose and present preliminary results on the migration of traffic lights as roadside-based infrastructures to in-vehicle virtual signs supported only by vehicle- to-vehicle communications. We design a virtual traffic light protocol that can dynamically optimize the flow of traffic in road intersections without requiring any roadside infrastructure. Elected vehicles act as temporary road junction infrastructures and broadcast traffic light messages that are shown to drivers through in-vehicle displays. This approach renders signalized control of intersections truly ubiquitous, which significantly increases the overall traffic flow. We pro- vide compelling evidence that our proposal is a scalable and cost-effective solution to urban traffic control.

Large-scale simulation of V2V environments

Providing vehicles with enhanced ability to communicate and exchange real-time data with neighboring vehicles opens up a variety of complex challenges that can only be met by combining different research fronts such as wireless communications, information processing, self-organization protocols and collaborative optimization. The difficulty in performing real tests in this area forces the use of computer simulation. In this paper we introduce an efficient simulation framework for large scale vehicle-to-vehicle (V2V) networks in urban environments. Our main contribution is a sophisticated traffic simulator, which is oriented towards simulating car-to-car communications, and relies on a global positioning server in order to convey location information for micro-simulated vehicles. To illustrate the various studies made possible by our simulation system, we provide a preliminary characterization of how the wireless transmission range in an urban-like environment affects the freshness and inter-vehicle propagation characteristics of real-time mobility information.

Stereoscopic aerial photography: an alternative to model-based urban mobility approaches

In the absence of large-scale deployments of VANETs, simulation based research is until now the only choice available to address and validate the design of protocols in the context of vehicular networks. The simulation frameworks involved in this research have to model two essential components, namely the vehicular mobility and the wireless inter-vehicle communication. Both of these aspects are especially complex in urban scenarios. In this paper we propose an alternative approach to obtain a realistic configuration of vehicles, and the respective traveling speeds, based on stereoscopic aerial photography, that is available to virtually every city in the world. We further use the aerial perspective of an urban area to identify a buildings layer and evaluate a wireless communication model that accounts for the obstructions caused by such layer on the connectivity of the wireless network. We evaluate our proposal over the city of Porto and compare the results obtained with model-based mobility approaches. Our results show significant differences in the connectivity profile of the analyzed urban VANET.

On the Urban Connectivity of Vehicular Sensor Networks

Aiming at a realistic mobile connectivity model for vehicular sensor networks in urban environments, we propose the combination of large-scale traffic simulation and computational tools to characterize fundamental graph-theoretic parameters. To illustrate the proposed approach, we use the DIVERT simulation framework to illuminate the temporal evolution of the average node degree in this class of networks and provide an algorithm for computing the transitive connectivity profile that ultimately determines the flow of information in a vehicular sensor network.

A Cautionary View of Mobility and Connectivity Modeling in Vehicular Ad-Hoc Networks

Motivated by the recent surge in vehicular ad-hoc network (VANET) research and the promise of high-impact applications such as safety, navigation and infotainment services, we consider the impact of mobility mis-modeling on the design and development of this class of distributed systems. Focusing on urban environments, we use a state-of-the-art car traffic simulator to extract some of the key connectivity metrics relevant for the design of a vehicle-to-vehicle traffic information system. We compare such metrics against those obtained from popular mobility models, such as the random waypoint model and the Manhattan mobility model. Our results reveal striking differences in the connectivity profile of the network, thus casting some doubt on the adequacy of simple mobility models for the development of future VANET protocols.

Self-automated parking lots for autonomous vehicles based on vehicular ad hoc networking

Parking is a major problem of car transportation, with important implications in traffic congestion and urban landscape. Reducing the space needed to park cars has led to the development of fully automated and mechanical parking systems. These systems are, however, limitedly deployed because of their construction and maintenance costs. Leveraging on semi and fully-autonomous vehicular technology, as well as on the electric propulsion paradigm and in vehicular ad hoc networking, we propose a new parking concept where the mobility of parked vehicles is managed by a parking lot controller to create space for cars entering or exiting the parking lot, in a collaborative manner. We show that the space needed to park such vehicles can be reduced to half the space needed with conventional parking lot designs. We also show that the total travelled distance of vehicles in this new parking lot paradigm can be 30% less than in conventional parking lots. Our proposal can have important consequences in parking costs and in urban landscape.

Virtual traffic lights in partial deployment scenarios

Vehicular ad hoc networks (VANETs) are seen as an important enabling technology for improving both traffic safety and efficiency. Virtual Traffic Lights (VTLs) are a promising proposal for reducing travel time by efficiently controlling road intersections. VTLs use vehicle-to-vehicle communication to dynamically optimize traffic flow and they display traffic light information on the windshield. However, research so far has assumed that all vehicles are equipped with VTL support and it has ignored the incremental deployment phase, which could last decades. In this paper we present a solution for a VTL partial deployment scenario that is based on the idea of having VTL equipped cars display traffic light information on the outside of the vehicle. This allows drivers in non-equipped vehicles, or even pedestrians, to see the light color and respond accordingly. We show that the benefits of VTLs in terms of intersection throughput and average delay reduction grow as a function of the penetration rate of equipped vehicles.

Urban Connectivity Analysis of VANETs through Stereoscopic Aerial Photography

Connectivity analysis of Vehicular Ad Hoc Networks (VANETs) involves the study of static and dynamic characteristics of the network. Realistic mobility models are essential for both aspects, in order to produce valid configurations of the position of vehicles in one static instant, and to dynamically move such vehicles in an interval of time. Focusing on static connectivity evaluation, we extend the state-of-the-art of the realism of urban mobility models for VANETs, by proposing and implementing an analysis based on a stereoscopic aerial survey over a large European city. Our static connectivity metrics show important differences compared to the model and simulation based results described in the VANET literature.

Locating cars through a vision enabled VANET

With the introduction of cameras in production cars, and the wide dissemination of wireless inter-vehicle communication devices in all new vehicles in the foreseeing future, emerging applications of this “omnipresent hardware network” can be designed. That is the case of the localization process of a particular vehicle, as the result of a broadcasted search warrant from some particular authority. The system here proposed relies in the optical recognition of the license plate of the wanted car. We present some results of license plate recognition based on real-world images acquired in different driving conditions, as well as of simulation of such a distributed search in a large-scale urban VANET, that show the feasibility of the whole process. A cryptographic protocol is proposed to deal with the security issues of the system.

Vehicular Sensing: Emergence of a Massive Urban Scanner

Vehicular sensing is emerging as a powerful mean to collect information using the variety of sensors that equip modern vehicles. These sensors range from simple speedometers to complex video capturing systems capable of performing image recognition. The advent of connected vehicles makes such information accessible nearly in real-time and creates a sensing network with a massive reach, amplified by the inherent mobility of vehicles. In this paper we discuss several applications that rely on vehicular sensing, using sensors such as the GPS receiver, windshield cameras, or specific sensors in special vehicles, such as a taximeter in taxi cabs. We further discuss connectivity issues related to the mobility and limited wireless range of an infrastructure-less network based only on vehicular nodes.