Eugenio Giordano

CORNER: a realistic urban propagation model for VANET

Recent advances in portable technologies suggest that ad hoc networks will finally move out from the research and military harbors to the commercial world. In particular, vehicular safety and entertainment applications are mature for the market. Several major manufacturer are considering vehicular communications as an opportunity to increase the profitability and marketability of their vehicles. In this phase, simulations are essential to evaluate the performance of protocols and applications large urban Ad Hoc and Vehicular networks. This paper tackles on the long overdue issue of an high fidelity propagation model for urban ad hoc networks. In particular, we propose CORNER a low computational cost yet accurate urban propagation prediction technique for ad hoc networks in urban scenarios. We also provide validation of the model through a side-to-side comparison of real experiments and simulations.

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.

CORNER: A Radio Propagation Model for VANETs in Urban Scenarios

Advances in portable technologies and emergence of new applications stimulate interest in urban vehicular communications for commercial, military, and homeland defense applications. Simulation is an essential tool to study the behavior and evaluate the performance of protocols and applications in large-scale urban vehicular ad hoc networks (VANET). In this paper, we propose CORNER, a low computational cost yet accurate urban propagation model for mobile networks. CORNER estimates the presence of buildings and obstacles along the signal path using information extrapolated from urban digital maps. A reverse geocoding algorithm is used to classify the propagation situation of any two nodes that need to communicate starting from their geographical coordinates. We classify the relative position of the sender and the receiver as in line of sight (LOS) or nonline of sight (NLOS). Based on this classification, we apply different formulas to compute the path loss (PL) metric. CORNER has been validated through extensive on-the-road experiments, the results show high accuracy in predicting the network connectivity. In addition, on-the-road experiments suggest the need to refine the fading model to differentiate between LOS, and NLOS situations. Finally, we show the impact of CORNER on simulation results for widely used applications.

C-VeT the UCLA campus vehicular testbed: Integration of VANET and Mesh networks

Vehicular communications are becoming a reality under the push of increased transportation safety requirements and huge investments of several actors in the field like car manufacturers and Public Transport Authorities. As a consequence, the building blocks of the ”Vehicle Grid” (radios, Access Points, spectrum, standards, etc.) will soon be in place enabling a broad gamut of applications ranging from automatic safety systems, intelligent transport, entertainment, urban sensing and environmental protection/monitoring. In this paper, we take a visionary look at ”Vehicular Grid” and we argue that the cooperation of pure ad-hoc vehicle-to-vehicle communications and roadside infrastructure is fundamental to broaden the supported applications. The paper further describes the activities carried out at UCLA to deploy an open testbed integrating ad hoc vehicle-to-vehicle communications and a wireless mesh backhaul based on MobiMESH hardware/software solutions.

TrafRoute: A different approach to routing in vehicular networks

In the near future vehicular networks based on wireless technology will be part of our lives. Efficient and robust routing algorithms will play a key role in the success of such technology. In this paper we present TrafRoute, an efficient and robust routing scheme for vehicular networks, suitable for both Vehicle-to-Vehicle and Vehicle-to-Infrastructure communications. TrafRoute introduces a novel approach to routing that involves landmark-based routes and forwarder self-election, exploiting the knowledge of the underlying road network. We demonstrate TrafRoutes efficiency and robustness through simulation studies performed with accurate mobility and propagation models.

VANET: On Mobility Scenarios and Urban Infrastructure. A Case Study

In [1] we show how vehicles can opportunistically exploit infrastructure through open access points (APs) to efficiently communicate with other vehicles. We also highlight the importance of the use of a correct mobility model, since the advantages that may derive from the use of an infrastructure may not be appreciated because of a lack of accuracy. We continue our study based on realistic vehicular mobility traces of downtown Portland, Oregon, obtained from extremely detailed large scale traffic simulations performed at the Los Alamos National Laboratories (LANL). This mobility model is used to evaluate both flat and opportunistic infrastructure routing. We here build upon [1] and extend that work to: (a) assess the impact of a range of mobility models on network performance and; (b) discuss the performance trend we may expect during the day, as urban mobility patterns change. We here compare results obtained with CORSIM [2] traces and Random Waypoint (RWP) [3] to the results obtained with realistic mobility traces.

VERGILIUS: A Scenario Generator for VANET

Vehicular networks are on the fast track to become a reality either through a car manufacturer that introduces a communication device in the car electronics or through an aftermarket vendor such a GPS navigator or a in-vehicle entertainment system. This paper introduces VERGILIUS a nouvelle urban mobility and propagation toolbox designed to streamline the mobility trace generation and path loss computation in vehicular network studies. The aim of VERGILIUS is to enable a whole new level of simulation through the introduction of Urban Maps, finely tunable motion patterns, and detailed trace analysis.

Enhancing in vehicle digital maps via GPS crowdsourcing

In this paper, we propose a simple and effective method to extend digital maps with the location and timing of stop-signs and traffic lights in a city, given GPS traces collected by on-road vehicles. Our system finds the location and timing of traffic lights and stop-signs using a small number of traces per road segment. We developed and evaluated the system by applying it to two sets of GPS traces — open street map, a multicity, publicly available database of GPS traces, and a set of traces collected in west Los Angeles. Evaluation results show that our system can estimate the location of stop-signs with as little as 5 traversal per road segment and the location/timing of traffic lights with as little as 7 traversals, with more than 90% accuracy.

CORNER: a step towards realistic simulations for VANET

Advances in portable technologies and emergence of new applications stimulate interest in urban vehicular communications for commercial, military, and homeland defense applications. Simulation is an essential tool to study the behavior and evaluate the performance of protocols and applications in large-scale urban vehicular networks. In this paper we propose CORNER a low computational cost yet accurate urban propagation model for mobile networks. CORNER estimates the presence of buildings and obstacles along the signal path using information extrapolated from urban digital maps. A reverse geocoding algorithm is used to classify the propagation situation of any two nodes that need to communicate starting from their geographical coordinates. Sender and Receiver are classified as in Line of Sight if there are no obstacles in between, and as NON in Line of Sight when there are obstacles (i.e. buildings) between them. CORNER has been validated through extensive on-the-road experiments, the results show high accuracy in predicting the network connectivity. In addition, on-the-road experiments suggest the need to refine the fading model to differentiate between Line of Sight, and NON Line of Sight situations. Finally, we show the impact of CORNER on simulation results for widely used applications.

Two Ray or not Two Ray this is the price to pay

Simulation is essential to evaluate the performance of large scale vehicular networks. It is logistically challenging (and prohibitively expensive) to run tests with more than a few dozens experimental vehicles. Given the critical role of simulation in the evaluation of VANET protocols in large scale scenarios, it is important to guarantee realism of the models. This paper focuses on the accuracy of urban propagation models and their impact on vehicular protocol results. In a city-based vehicular network we compare the predominant Two Ray model and a recently proposed Corner model. We identify a number of factors that undermine the validity of the Two Ray model, for example, the presence of buildings causing propagation disruption and the heavy weight border effects that incorrectly compensate for the presence of hidden terminals in the networks. The paper analyzes a small scale urban vehicular scenario which unveils the issues to be considered in large scale vehicular simulations.