Popescu-Zeletin / Radusch / Rigani Vehicular-2-X Communication

State-of-the-Art and Research in Mobile Vehicular Ad hoc Networks
1. Auflage 2010
ISBN: 978-3-540-77143-2
Verlag: Springer
Format: PDF
Kopierschutz: 1 - PDF Watermark

E-Book, Englisch, 116 Seiten, eBook

Universal vehicular communication promises many improvements in terms of ac- dent avoidance and mitigation, better utilization of roads and resources such as time and fuel, and new opportunities for infotainment applications. However, before widespread acceptance, vehicular communication must meet challenges comparable to the trouble and disbelief that accompanied the introduction of traf c lights back then. The rst traf c light was installed in 1868 in London to signal railway, but only later, in 1912, was invented the rst red-green electric traf c light. And roughly 50 years after the rst traf c light, in 1920, the rst four-way traf c signal comparable to our today’s traf c lights was introduced. The introduction of traf c signals was necessary after automobiles soon became prevalent once the rst car in history, actually a wooden motorcycle, was constructed in 1885. Soon, the scene became complicated, requiring the introduction of the “right-of-way” philosophy and later on the very rst traf c light. In the same way the traf c light was a necessary mean to regulate the beginning of the automotive life and to protect drivers, passengers, as well as pedestrians and other inhabitants of the road infrastructure, vehicular communication is necessary to accommodate the further growth of traf c volume and to signi cantly reduce the number of accidents.

Zielgruppe

Research

Autoren/Hrsg.

Popescu-Zeletin, Radu

Radusch, Ilja

Rigani, Mihai Adrian

Inhaltsverzeichnis

Applications of Vehicular Communication.- Communication Regimes.- Information in the Vehicular Network.- Routing.- Medium Access for Vehicular Communications.- Physical Layer Technologies.- Security.

Leseproben

"Chapter 5 Routing (p. 67-68)

Routing refers to move a data packet from source to destination and if required the assignment of a path to the destination. In multi-hop regime routing means to forward packets that contain information through other vehicles [1]. This information refers to alerts about events that already happened, like local danger warnings and traffic flow information. If no vehicle is within the communication range a packet is stored and forwarded as soon as a new vehicle comes into reach. In multi-hop regime the information may be disseminated in two ways: to all surrounding nodes (multicast) or to the ones in a specific area (geocast). Nodes, by exchanging information about network links, compute the best path by which to route messages to other nodes.

Routing in highly mobile ad-hoc networks has to preserve the integrity of message information disseminated in the network while minimizing the number of propagations of each message. Different factors influence the message integrity, e.g. routing algorithm, environmental conditions (physical layer), but also intruder attacks (security). Several algorithms are presented below, and in order to compare them we introduce three vital parameters: PDR, latency and overhead. The PDR (Packet Delivery Ratio) [2, 3] represents the successfully received packets per sent packets. In theory, if no loss of messages occurs, this value should be 1.

In real tests this value is below 1 because in ad-hoc networks one big weakness is that route between a source and a destination is likely to have errors or even break during communication. It was demonstrated in [4] that the data packet loss rate can be decreased significantly by using relative local positions between nodes to discover routes and to make the routing decision for the ad-hoc network. The latency or end-to-end delay [5] represents the time delay from the source sending a packet to the destination receiving it. RTT (Round Trip Time) represents the latency plus time delay from destination back to source, also known as “ping”.

The routing overhead, which represents ratio of control data per payload data should be as low as possible to prevent excessive load of the network. The overhead can be reduced using location-based routing algorithms that may obtain absolute position from a positioning system such as Global Positioning System (GPS) or relative local position between nodes. Other important parameter in routing algorithms is the fault tolerance [6] that requires detection of and recovery from faults.

The above parameters can be unified under the so-called scalability effect. This effect [7–9] ensures adaptability and represents QoS (Quality of Service) impact (PDR, latency, overhead, fault tolerance, etc.) with the growth of network size. A scalable algorithm maintains its QoS parameters with the increase of the network. Routing with multi-hop position based regime is illustrated in Fig. 5.1. Different transmission strategies are possible: Either broadcast the message to all surrounding vehicles until the geocast region is reached, or create a path from source to the geocast region. Each transmission has its advantages and disadvantages. If a path is created, than less network load is required, but if the link is broken, information misses its target. If the flooding approach is used, then multiple paths exists. So, fault tolerance is provided, but also an increase of network load."

Über Autor(innen)

Radu Popescu-Zeletin is Professor at the Technical University Berlin, and, since its foundation, has been director of the Fraunhofer Institute for Open Communication Systems, FOKUS, (formerly a GMD Institute). For many years he was head of the Research and Development Department of the BERKOM project at Deutsche Telekom. He has published numerous articles on distributed computer systems and applications. He is an active member of numerous standardization committees and is a leading player in the development of telecommunication standards. As holder of the Chair of Open Communication Systems, he also plays a major role in the development of the vision of I-centric Communications. Prof. Popescu-Zeletin has been appointed chairman of the Scientific Advisory Council of DeTeCon International. As a member of the Motorola Visionary Board, he is one of 30 leading international experts helping to shape the future in the field of mobile communications. He has also been invited by the University of Technology, Tokyo to assume a full professorship; appointment formalities are now underway (early 2004). Prof. Popescu-Zeletin graduated at the Polytechnic Institute in Bucharest, Romania, gained his Ph.D. at the University of Bremen, and habilitated at the Technical University of Berlin. Prof. Popescu-Zeletin is Senior Member of the IEEE, Doctor honoris causa at the Polytechnic Institute in Bucharest, and Professor honoris causa at the Catholic University of Campinas, Brasil. Furthermore he is member of the Motorola Visionary Board 2004/2005 as well as member of the Rumanian Academy. Prof. Popescu-Zeletin is bearer of the Public Service Medal of the Republic of Romania Ilja Radusch received his M.Sc. in Computer Science from the University of Technology Berlin (TUB). Since 2003 he is researcher with the Open Communication Systems (OKS) as well as with Fraunhofer FOKUS since 2005. Since 2006 he is group leader at the Daimler Center for Automotive Information Technology Innovations (DCAITI). He is working in the field of Car-2-Car Communication, Sensor and Ad-hoc Networks, and Context-aware Services. His responsibility includes several projects for industry partners such as Deutsche Telekom and DaimlerChrysler as well as research projects for the German Ministry of Education and Research and the European Union. Furthermore, he is giving various lecture courses at the TU Berlin Mihai Adrian Rigani received his degree in Electrotechnics in 2005 at Polytechnic University of Bucharest. Since then he is research scientist with the Daimler Center for Automotive Information Technology Innovations (DCAITI) at the Open Communication Systems (OKS) department of the Technische Universität Berlin (TUB).