Gustavo Marfia

Will IPTV ride the peer-to-peer stream? [Peer-to-Peer Multimedia Streaming]

The great success of P2P systems for the purpose of file-sharing set the path to the next killer application on the Internet, P2P video streaming. Although it solves scalability issues, P2P technology experiences problems of a long start time and churn-induced instability that can greatly affect the user experience. Moreover, technical and business solutions for digital rights management are still under investigation. Great efforts are underway in both academia and industry to solve these problems, whose solution will offer a scalable, affordable, and legal TV-quality-like broadcast of content. In this article, we analyze what is available to the end user in terms of P2P video-streaming products and determine which of these are the most promising for IPTV and content distribution companies. In the following, we offer: (1) A survey of the available architectures. (2) A set of experiments on a popular peer-to-peer system, SopCast. (3) Guidelines for large scale deployment.

On the Effectiveness of an Opportunistic Traffic Management System for Vehicular Networks

Road congestion results in a huge waste of time and productivity for millions of people. A possible way to deal with this problem is to have transportation authorities distribute traffic information to drivers, which, in turn, can decide (or be aided by a navigator) to route around congested areas. Such traffic information can be gathered by relying on static sensors placed at specific road locations (e.g., induction loops and video cameras) or by having single vehicles report their location, speed, and travel time. While the former approach has been widely exploited, the latter has come about only more recently; consequently, its potential is less understood. For this reason, in this paper, we study a realistic test case that allows the evaluation of the effectiveness of such a solution. As part of this process, (a) we designed a system that allows vehicles to crowd-source traffic information in an ad hoc manner, allowing them to dynamically reroute based on individually collected traffic information; (b) we implemented a realistic network-mobility simulator that allowed us to evaluate such a model; and (c) we performed a case study that evaluates whether such a decentralized system can help drivers to minimize trip times, which is the main focus of this paper. This study is based on traffic survey data from Portland, OR, and our results indicate that such navigation systems can indeed greatly improve traffic flow. Finally, to test the feasibility of our approach, we implemented our system and ran some real experiments at UCLAs C-Vet test bed.

Evaluating vehicle network strategies for downtown Portland: opportunistic infrastructure and the importance of realistic mobility models

In an urban environment, vehicles can opportunistically exploit infrastructure through open Access Points (APs) to efficiently communicate with other vehicles. This is to avoid long wireless ad hoc paths, and to alleviate congestion in the wireless grid. Analytic and simulation models are used to optimize the communications and networking strategies. For realistic results, one important challenge is the accurate representation of traffic mobility patterns. In this paper we introduce realistic vehicular mobility traces of downtown Portland, Oregon, obtained fromextremely detailed large scale traffic simulations performed at the Los Alamos National Laboratories (LANL). To the best of our knowledge, these are among the most accurate synthetic motion traces available for study, with the exception of actual car trace measurements. The new mobility model is used to evaluate AODV [1] in flat and opportunistic infrastructure routing. To assess the importance of a realistic mobility model for this evaluation, we compare these results with those obtained with CORSIM [2] traces. The paper makes the following contributions: (a) introduction of efficient, opportunistic strategies for extending the AP infrastructure to use vehicle to vehicle paths, and (b) assessment of different mobility models - CORSIM traces and LANLs realistic vehicular traces - in the modeling of different routing strategies.

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.

Realizing the unexploited potential of games on serious challenges

Author address: University of Padua - Pure and Applied Mathematics, Via Trieste, 63 Padova, D 35131, Italy Permission to make digital or hard copies of part or all of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies show this notice on the first page or initial screen of a display along with the full citation. Copyrights for components of this work owned by others than ACM must be honored. Abstracting with credit is permitted. To copy otherwise, to republish, to post on servers, to redistribute to lists, or to use any component of this work in other works requires prior specific permission and/or a fee. Permissions may be requested from Publications Dept., ACM, Inc., 2 Penn Plaza, Suite 701, New York, NY 10121-0701 USA, fax +1 (212) 869-0481, or permissions@acm.org. ©2010 ACM 1544-3574/2010/12-ART23

TCP at last: reconsidering TCP's role for wireless entertainment centers at home

10.00 DOI: 10.1145/1921141.1921143 http://doi.acm.org/10.1145/1921141.1921143 ACM Computers in Entertainment, Vol. 8, No. 4, Article 23, Publication date: December 2010

The art and craft of making the Tortellino: playing with a digital gesture recognizer for preparing pasta culinary recipes

The amount of investments and research that led to the launch of new high definition TV sets and game consoles witness the importance gained by the home entertainment segment of the consumer market. Moreover, many entertainment appliances connect wireless to the Internet, providing users with the freedom of enjoying them at their preferred location at home. As this happens, there has been a widespread interest for the design of Home Entertainment Centers (HECs). HECs play, in fact, a key role as they are the media gateways between the home appliances and the Internet, thus enabling the distribution of various services based on different media streams at home. As most media flows are today based on the Transmission Control Protocol (TCP), and most entertainment services are distributed via wireless, wireless HEC designers face the problem of devising a protocol architecture that avoids the disruption of media flows and, consequently, of multimedia services. We here propose a solution to this problem and support its effectiveness with both analytical and simulation results.