Improving Highway Traffic through Partial Velocity Synchronization

in Proceedings of the IEEE Global Communications Conference 2012 (2012)

In this paper we address the problem of uncoor- dinated highway traffic. We first identify the main causes of the capacity drop, namely high traffic demand and inadequate driver reaction. In the past ... [more ▼]

In this paper we address the problem of uncoor- dinated highway traffic. We first identify the main causes of the capacity drop, namely high traffic demand and inadequate driver reaction. In the past, traffic and user behavior have been accurately described by cellular automata (CA) models. In this paper we extend the CA model to deal with highway traffic fluctuations and jams. Specifically, the model incorporates the communication layer between vehicles. The model thus enables us to study the impact of inter-vehicular communications and in particular the delivery of critical and timely upstream traffic information on driver reaction. Based on the newly-available traffic metrics, we propose an Advanced Driver Assistance System (ADAS) that suggests non-intuitive speed reduction in order to avoid the formation of so-called phantom jams. The results show that using such a system considerably increases the overall traffic flow, reduces travel time and avoids unnecessary slow-downs. [less ▲]

CORNER: A Radio Propagation Model for VANETs in Urban Scenarios

in Proceedings of the IEEE (2011), 99(7), 1280-1294

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 ... [more ▼]

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. [less ▲]

Efficient Data Dissemination Techniques For Multi-Hop Wireless Networks Applied to Vehicular Communications

Doctoral thesis (2010)

Multi-Hop Wireless Networks (MHWN) are composed of devices called nodes, which communicate in an ad hoc fashion. Such networks allow the relaying of transmissions over multiple wireless hops to provide an ... [more ▼]

Multi-Hop Wireless Networks (MHWN) are composed of devices called nodes, which communicate in an ad hoc fashion. Such networks allow the relaying of transmissions over multiple wireless hops to provide an extended service area. There are two main classes of MHWN. The first includes all networks that have a static network topology, e.g. Wireless Mesh Networks and Wireless Sensor Networks. The second specifies networks with a dynamic or mobile topology, e.g. Vehicular Networks. For both types, collaborative applications are of great importance. In such a scenario, information needs to be made available to multiple, or sometimes all nodes in the network. The trivial method, pure network flooding, is to retransmit the information at every hop exactly once. In previous studies it has been shown that such an approach considerably lowers the overall performance of the network by saturating the shared communication channel. In this thesis, we present two different approaches that perform efficient data dissemination among collaborative nodes in MHWNs. The primarily objective is to reduce the number of redundant retransmissions by selecting only a subset of nodes to be responsible for relaying the information without compromising global delivery. We propose one approach for each of the two classes using different methodologies. For static network topologies, we present a novel heuristic based on the Minimum Connected Dominating Set problem. This approach allows the election of a near-optimal set of relays that are able to reach every other node in the network, thus minimizing the number of retransmissions. We theoretically and experimentally validate our approach and compare it to other state-of-the-art dissemination techniques. For dynamic network topologies, we focus primarily on Vehicular Networks. We present a new routing protocol that makes use of an efficient dissemination technique to find robust communication paths between two vehicles. Strategic vehicles are elected as relays based on their position and on information about the local neighborhood. The protocol is evaluated using a novel simulation framework that takes into account specific characteristics of vehicular networks in urban environments, e.g. mobility of the vehicles and signal propagation. The performance evaluation shows that our protocol introduces only a low control overhead and provides robust communication paths that achieve high delivery ratios. [less ▲]

TrafRoute: A Different Approach to Routing in Vehicular Networks

in Proceedings of the IEEE 6th International Conference on Wireless and Mobile Computing, Networking and Communications (WiMob) (2010)

CORNER: A Step Towards Realistic Simulations for VANET

in Proceedings of the seventh ACM international workshop on VehiculAr InterNETworking (2010)

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

in Proceedings of the IEEE 6th International Conference on Mobile Adhoc and Sensor Systems (MASS '09) (2009)

Tree Based Flooding Protocol for Multi-Hop Wireless Networks

in Proceedings of the 3rd International Conference on Broadband Communications, Information Technology & Biomedical Applications (2008)