Abstract

Part 6: New Testing Methods; International audience; In this paper, we focus on Mobile Ad-hoc Networks (MANETs) with non-uniform node density distribution such as Vehicular Ad-hoc Networks (VANETs) and Delay Tolerant Networks (DTNs), and propose a technique for protocol testing and performance evaluation. In such MANETs, node density varies depending on locations and time, and it dynamically changes every moment. In the proposed method, we designate node density distributions and their dynamic variations in a target area. Then, we construct a graph called TestEnvGraph where all node density distributions are treated as its nodes and they are connected by edges whose weights denote differences of two node density distributions. We specify a set of edges to be tested in the graph, formulate a problem for efficiently reproducing all the given node density distributions and their dynamic variations as a rural postman problem, find its solution and use it as the order of reproduction of designated node density distributions and their variations. Protocol testing is carried out by reproducing node density distributions in the derived order. We have designed and developed a method and its tool for mobility generation on MANETs, which can reproduce any designated node density distribution and its dynamic variations in a target area. From our experiments for a VANET protocol, we have shown that our method can give a similar trend in network throughput and packet loss rates compared with realistic trace based protocol testing. Document type: Part of book or chapter of book

Abstract

An Intelligent Transportation System (ITS) is a system based on wireless communications which has been investigated for many years in order to provide new technologies able to improve safety and efficiency of road transportation with integrated vehicle and road systems. It combines all aspects of technology and systems design concepts in order to develop and improve transportation system of all kinds. ITS, which utilise information and communications technology in vehicle as well as within the roadside infrastructure, can also be used to improve mobility while increasing transport safety, reducing traffic congestion, maximising comfort, and reducing environmental impact (Andrisano et al., 2000). Intelligent transportation systems and applications can improve the quality of travel by selecting routes with up-to-the-minute information data, giving priority to response vehicle teams, notifying drivers about road incidents, and delivering ITS services to drivers. They can reduce fuel consumption by routing the vehicles to their destinations so that fuel waste is significantly reduced, and also fully utilise the capacity of the existing road vehicular networks by controlling the flow of vehicles based on traffic monitoring and detecting congestions. Document type: Part of book or chapter of book

Abstract

This paper presents an approach for coupling traffic simulators of different resolutions in order to conduct virtual evaluations of advanced driver assistance systems based on vehicular ad hoc networks that are both large scale and a high fidelity. The emphasis is put on the need for such an attempt to satisfy the constraint of performing simulations in real time. Both the methods to accomplish this as well as the resulting performance are described. Document type: Part of book or chapter of book

Abstract

International audience; The experimental evaluation of wireless and mobile networks is a challenge that rarely substitutes simulation in research works. This statement is even more evident in vehicular communications, due to the equipment and effort needed to obtain significant and realistic results. In this paper, key issues in vehicular experimental evaluation are analyzed by an evaluation tool called AnaVANET, especially designed for assessing the performance of vehicular networks. This software processes the output of well-known testing tools such as ping or iperf, together with navigation information, to generate geo-aware performance figures of merit both in numeric and graphical forms. Its main analysis capabilities are used to validate the good performance in terms of delay, packet delivery ratio and throughput of NEMO, when using a road-side segment based on IPv6 GeoNetworking. Document type: Part of book or chapter of book

Abstract

The final publication is available at Springer via http://dx.doi.org/10.1007/978-3-642-39247-4_6 Road traffic is experiencing a drastic increase in recent years, thereby increasing the every day traffic congestion problems, especially in cities. Vehicle density is one of the main metrics used for assessing the road traffic conditions. Currently, most of the existing vehicle density estimation approaches, such as inductive loop detectors or traffic surveillance cameras, require infrastructure-based traffic information systems to be installed at various locations. In this paper, we present I-VDE, a solution to estimate the density of vehicles that has been specially designed for Vehicular Networks. Our proposal allows Intelligent Transportation Systems to continuously estimate the vehicular density by accounting for the number of beacons received per Road Side Unit, as well as the roadmap topology. Simulation results indicate that our approach accurately estimates the vehicular density, and therefore automatic traffic controlling systems may use it to predict traffic jams and introduce countermeasures. Barrachina Villalba, J.; Garrido Picazo, MP.; Fogue, M.; Martínez, FJ.; Cano Escribá, JC.; Tavares De Araujo Cesariny Calafate, CM.; Manzoni, P. (2013). I-VDE: A Novel Approach to Estimate Vehicular Density by Using Vehicular Networks. En Ad-hoc, Mobile, and Wireless Network. Springer. 63-74. doi:10.1007/978-3-642-39247-4_6 Senia 63 74 Document type: Part of book or chapter of book

Abstract

In vehicular ad hoc networks (VANETs), successful delivery of GeoUnicast and GeoBroadcast packets depends on scenario-specific aspects like vehicle density, distribution of vehicles on the road and type of the environment (e.g., urban, rural). These aspects can significantly influence the reliability of the connection between communication parties making traditional ITS-G5 based ad hoc networks unreliable. The absence of communication partners in range, long transmission distances, non-line-of-sight (NLOS) conditions are just a few examples that could hinder ITS-G5 transmissions. In this paper, we propose a Hybrid Policy-based Network Selection Algorithm that uses LTE to strengthen and complement ITS-G5 under critical conditions in which successful transmission over the ad hoc network is highly unlikely. The main objective is to use as less LTE transmissions as possible whilst maintaining high Packet Delivery Ratio (PDR) within defined delay constraints. The results, which are derived from extensive simulation campaigns, show a clear advantage of using the hybrid scheme over solely ITS-G5 or LTE. Document type: Conference object

Abstract

Vehicular ad hoc networks (VANETs), often called Car2X communication systems, are about to enter the mass market in upcoming years. They are intended to increase traffic safety by enabling new safety critical driver assistance systems. This also means that strong security mechanisms are required to safeguard communication within VANETs. However, standardized security mechanisms lead to significant overhead in terms of data rate requirement and delay. Prior work has focused on reducing the overhead by advanced strategies for pseudonym and authorization authority certificate exchange. However, we find that this is not enough to enable reliable message exchange in VANETs. Various other sources of overhead caused by security mechanisms in VANETs are identified in the provided analysis. Thereby, we find cross layer and cross message dependencies. In combination with the non-fragmentation property of VANET messages, such dependencies are discovered to lead to massive dropping of packets due to maximum size violations at low protocol layers. Thus, we develop a method for cross layer on demand content assembling for VANET messages, which can avoid the size limit violations without preventing individual layers from disseminating their variable length data sets.

Abstract

Car-to-X communication systems, often called vehicular ad-hoc networks (VANETs), are in the process of entering the mass market in upcoming years. Thereby, security is a core point of concern due to the intended use for safety critical driver assistance systems. However, currently suggested security mechanisms introduce significant overhead into Car-to-X systems in terms of channel load and delay. Especially, the usage of on the fly distributed pseudonym certificates leads to a trade off between channel load and authentication delay, which may lead to significant packet loss. Thus, this work studies a novel concept for pseudonym certificate distribution in VANETs using rate-adaptive certificate distribution based on monitoring a vehicle's environment. Thereby, the cyclic certificate emission frequency is adapted on the fly based on cooperative awareness metrics for discrete parts of the vehicle's surrounding. The obtained mechanism is evaluated in a highway as well as an urban simulation scenario to show its suitability for a broad range of traffic conditions. Thereby, we find that it is able to significantly outperform the currently standardized approach for pseudonym certificate distribution in VANETs based on ETSI ITS standards. Thus, it should be regarded for further development of future VANETs.