Marco Roccetti

An Intervehicular Communication Architecture for Safety and Entertainment

Intervehicle communication (IVC) is emerging in research prominence for the interest that it is generating in all major car manufacturers and for the benefits that its inception will produce. The specific features of IVC will allow the deployment of a wide set of possible applications, which span from road safety to entertainment. Even if, on the one hand, these applications share the common need for fast multihop message propagation, on the other hand, they possess distinct characteristics in terms of generated network traffic. The state of the art of current research only proposes solutions specifically designed for a single application (or class) that is not directly extendable to a general IVC context. Instead, we claim that a privileged architecture exists, which is able to support the whole spectrum of application classes. To this aim, we propose a novel IVC architecture that adapts its functionalities to efficiently serve applications by quickly propagating their messages over a vehicular network. We conducted an extensive set of experiments that demonstrate the efficacy of our approach. As representative case studies, we considered two application classes that, for their network traffic characteristics, are at the opposite boundaries of the application spectrum: safety and entertainment.

A theory of processes with durational actions

A new bisimulation-based semantics, called performance equivalence, is proposed for a process algebra equipped with TCSP parallel operator. This semantics relies on the basic assumption that actions are time-consuming, where their duration is statically fixed. Performance equivalence equates systems whenever they perform the same actions in the same amount of time, thus introducing a simple form of performance evaluation in process algebras. A comparison with other equivalences is provided; in particular, we show that performance equivalence is strictly finer than step bisimulation equivalence and strictly coarser than partial ordering bisimulation equivalence.

How Do You Quickly Choreograph Inter-Vehicular Communications? A Fast Vehicle-to-Vehicle Multi-Hop Broadcast Algorithm, Explained

As the technology available on cars is increasing, a wide range of applications, from safety to entertainment, are becoming factually accessible to passengers. Many of these applications involves a one-to-many transmission model where a single car broadcasts a message that has to be forwarded, even with multiple hops, in a very short time to all the other cars located within a range of few kilometers from the source. Since the high mobility and density of a car network scenario, specific solutions need to be devised to choreograph a fast-delivery multi- hop broadcast. To this aim, we developed a practical and efficient technique that allows cars to estimate their communication range with the help of a very limited message exchange and exploit this information to reduce the number of transmissions, as well as the hops to be traversed, and hence the time, required by a broadcasted message to reach all the cars following the sender within a certain distance.

Going Realistic and Optimal: A Distributed Multi-Hop Broadcast Algorithm for Vehicular Safety

A subject of great interest and important investments by governments, navigation system companies and street management authorities is highway safety. In this context, an important role is played by applications designed to warn drivers of upcoming dangers. An example is vehicular accident warning systems, which advertise accident events to approaching vehicles. The effectiveness of currently in use vehicular accident warning systems can be jeopardized by their: (a) inability to provide an accident warning to the closest approaching vehicles; and, (b) high delays in advertising an event. In fact, such systems are unable to reach the vehicles that are closest to an accident site due to the absence of any deployed automatic detection and broadcast mechanisms. The future deployment of Vehicular Ad hoc Networks (VANETs) can fill this gap. By leveraging on the distributed nature of ad hoc networks, accident warning systems can rapidly alert the vehicles which most risk their involvement in a crash. To reach this goal, VANET-based accident warning systems require the design of efficient broadcast algorithms. A number of solutions have been proposed in the past few years. However, no such proposals, to the best of our knowledge, assume realistic wireless propagation scenarios. The scope of this paper is to present an optimal distributed algorithm, working at the application layer, for the broadcast of safety messages in VANETs. Optimality, in terms of delay, is achieved in unidimensional highway scenarios and under realistic wireless propagation assumptions. This is the only algorithm, to this date, capable of reaching all vehicles with the minimum number of transmissions within a realistic setting.

Playing into the wild: A gesture-based interface for gaming in public spaces

Gestural-based interfaces have become one of the fundamental technologies that can determine the success of new computer games. In fact, computer games today offer interaction paradigms that go well beyond the use of remote controls, letting players directly perform exchanges with the objects and characters that compose the virtual worlds that are displayed in front of them. To perform such exchanges, new algorithms and technologies have been devised which include advanced visual recognition schemes, new video cameras and accelerometer sensors. At the same time, other important trends are also quietly emerging in the same domain: game designers, in fact, are slowly shifting their attention out of the walls of gaming fanatics homes, broadening their interests to computer games that can be played in public spaces, as exhibitions and museums. However, to the best of our knowledge, only a very limited amount of research experiences have taken into account the problem of producing computer games, based on gesture-based interfaces that well suit such settings. Hence, in this paper we address the problem of differentiating the design of a gesture-based interface for a console from the problem of designing it for a public space setting. Moreover, we will show that within a public space, it is possible to narrow down the vision algorithms that can well support the recognition of complex actions, whereas solely relying on a simple webcam. In particular, we will describe the design and implementation of an interface that well suits public immersive scenarios, since it is based on a simple and efficient set of algorithms which, combined with the intelligence given by the knowledge of the context of where a game is played, leads to a fast and robust interpretation of hand gestures. To witness this last aspect, we will report on the results obtained from the deployment of a computer game we specifically developed for public spaces, termed Tortellino X-Perience, which has been enjoyed by hundreds of visitors at the 2010 Shanghai World Expo.

Safe Driving in LA: Report from the Greatest Intervehicular Accident Detection Test Ever

The UN Economic Commissions Statistics of Road Traffic Accidents report of 2011 shows that every year, about 150 000 human beings lose their lives on the roads of the western world. Although it is a common belief that this figure could shrink with the use of new sensor and communication technologies, unfortunately, none such systems have hit the road to date. Ideally, if such technologies were put into place, vehicles could be part of a vehicular ad hoc network (VANET) capable of spreading relevant information about dangerous events (e.g., car accidents) to all approaching drivers. However, all this is mainly supported by simulation studies, as no practical results have been published to date, revealing the effective performances of such systems at work. In this paper, we fill this gap, presenting a detailed description of the greatest experiments (a few thousand throughout the streets of Los Angeles), to date, ever performed with an accident warning system specifically devised for highway scenarios. In particular, among all the possible candidate schemes, we ran a few thousand experiments with the accident warning system algorithm that was proven to be optimal in terms of bandwidth usage and covered distance in realistic scenarios. Our experiments confirm what has been observed before in theory and simulation, i.e., the use of such a system can reduce, by as much as 40%, the amount of vehicles involved in highway pileups.

Vehicular Congestion Detection and Short-Term Forecasting: A New Model With Results

While vehicular congestion is very often defined in terms of aggregate parameters, such as traffic volume and lane occupancies, based on recent findings, the interpretation that receives most credit is that of a state of a road where traversing vehicles experience a delay exceeding the maximum value typically incurred under light or free-flow traffic conditions. We here propose a new definition according to which a road is in a congested state (be it high or low) only when the likelihood of finding it in the same congested state is high in the near future. Based on this new definition, we devised an algorithm that, exploiting probe vehicles, for any given road 1) identifies if it is congested or not and 2) provides the estimation that a current congested state will last for at least a given time interval. Unlike any other existing approach, an important advantage of ours is that it can generally be applied to any type of road, as it neither needs any a priori knowledge nor requires the estimation of any road parameter (e.g., number of lanes, traffic light cycle, etc.). Further, it allows performing short-term traffic congestion forecasting for any given road. We present several field trials gathered on different urban roads whose empirical results confirm the validity of our approach.

Design and Experimental Evaluation of an Adaptive Playout Delay Control Mechanism for Packetized Audio for Use over the Internet

We describe the design and the experimental evaluation of a playout delay control mechanism we have developed in order to support unicast, voice-based audio communications over the Internet. The proposed mechanism was designed to dynamically adjust the talkspurt playout delays to the traffic conditions of the underlying network without assuming either the existence of an external mechanism for maintaining an accurate clock synchronization between the sender and the receiver during the audio communication, or a specific distribution of the audio packet transmission delays. Performance figures derived from several experiments are reported that illustrate the adequacy of the proposed mechanism in dynamically adjusting the audio packet playout delay to the network traffic conditions while maintaining a small percentage of packet loss.

Path 2.0: A participatory system for the generation of accessible routes

From the advent of the digital era, new powerful technologies have shown, on one hand, important progresses towards the mankind necessity and, on the other hand, a progressive isolation of individuals. In this work, we present a social application we have developed to support people with disabilities. Our application leverages on the popularity of smart phones and on the Web 2.0 paradigm to pervasively and invisibly collect information about the accessibility of city roads. This information is then used to provide a Google Maps-like service to determine an accessible path between any two locations for users with a certain disability.

Interactivity-loss avoidance in event delivery synchronization for mirrored game architectures

Since the expansion of their market and their challenging requirements, massively multiplayer online games are gaining increasing attention in the scientific community. One of the key factors in this kind of application is represented by the ability to rapidly deliver game events among the various players over the network. Employing in this context mirrored game server architectures and adapting RED (random early detection) techniques borrowed from network queuing management, we are able to show sensible benefits in upholding interactivity and scalability, whilst preserving game state consistency and game evolution fluency at the players side