Reinhold Eberhardt

Geocast in vehicular environments: caching and transmission range control for improved efficiency

Geocast in vehicular ad hoc networks allows to realize applications like virtual warning signs for improved road safety, which address a geographical area rather than an individual vehicle. In this paper we propose to include caching in the geocast forwarding scheme and improved neighborhood selection to address in particular the high velocities of vehicles. High velocities of vehicular networks are a major difference to usual mobile ad hoc networks which assume only moderate node movement. We show that a cache for presently unforwardable messages caused by network partitioning or unfavorable neighbors can significantly improve the geocast delivery success ratio. The improved neighborhood selection taking frequent neighborhood changes into account significantly decreases network load and decreased end-to-end delivery delay.

CGGC: Cached Greedy Geocast

With cached greedy geocast, we propose an enhanced forwarding scheme for geocast especially in highly mobile ad hoc networks. We will show, that a cache for presently unforwardable messages during what we call the line forwarding, can significantly improve the geocast delivery success ratio, especially in sparse peopled networks with high node velocities. Therefore, we introduce and examine two separate caching strategies and present simulation results in conjunction with geocast. Our simulations inquire the delivery success ratio but also the trade–off in delivery delay.

Time-stable geocast for ad hoc networks and its application with virtual warning signs

Virtual warning signs allow to increase road safety. Like real traffic or warning signs, they are attached to a certain geographical position or area. When a vehicle enters this area, the virtual warning sign is displayed for the driver. In contrast to real traffic signs they allow faster adaptation to the current road and traffic situation like icy roads or accident warnings. For the realization of virtual warning signs, geocasting is a promising approach. Existing geocast solutions lack the time-stability required for realizing virtual warning signs, which we call abiding geocast. An abiding geocast solution delivers a message either periodically or on demand, everytime a new vehicle enters the warning sign area. This article introduces the virtual warning sign idea and discusses the design space, three reasonable solutions and simulation results for abiding geocast in an ad hoc network. The first approach is an infrastructure-based server solution to store the messages. The second is an infrastructure-less approach that maybe more suitable for an ad hoc network. A node inside the geocast destination region is elected to act temporarily as a server for geocast messages. The last approach works infrastructure-less, too, by complementing the exchange of neighbor information necessary for many geographic unicast routing protocols with geocast information. In simulations we compare the delivery ratio and the resulting network load of the three approaches.

Performance evaluation of stored geocast

This paper presents a definition, the design space, three reasonable implementations, and an ns-2 simulation study of a new type of geocast protocol, called stored geocast. A stored geocast is a time stable geocast, which is delivered to all nodes that are inside a destination region within a certain period of time. When used in a mobile ad hoc network (MANET) it allows to realize a persistent message valid for a certain geographic region, possibly combined with a time limit. Stored geocast is of particular interest in the automotive domain, since it allows realizing virtual traffic signs or for location-based services in general. The simulation results investigate the delivery success ratio and the resulting message overhead in several scenarios with random waypoint movement and in realistic vehicular traffic scenarios gathered from a driver behavior simulator.

Eine Dienstgüteabbildungs- und -steuerungsarchitektur zur Gewährleistung unterschiedlicher Dienstgüteklassen für Ferntraining und -lernen

Die Bereitstellung von Trainings- und Lerninhalten am Arbeitsplatz bzw. in der Nahe des Arbeitsplatzes uber unternehmensinterne Kommunikationssysteme ist eine zunehmend wichiger werdende Erganzung zum bisherigen Schulungs- und Trainingsangebot fur das lebenslange Lernen der Mitarbeiter eines Unternehmens. Die Kommunikationssysteme und verteilten Anwendungen fur Ferntraining und -lernen mussen in der Lage sein, multimediale Inhalte in verschiedenen Qualitatsstufen zum Lernenden zu bringen. Da heute in Unternehmen eingesetzte Kommunikationsinfrastrukturen meistens nicht in der Lage sind, den Dienstguteanforderungen solcher Anwendungen gerecht zu werden, mussen im Gesamtsystem aus Kosten- und technischen Grunden dedizierte Kommunikationssysteme eingesetzt werden. Um die verschiedenen Klassen von Dienstgute, die von den Kommunikationssystemen angeboten werden, zu beherrschen, ist es sinnvoll, den eigentlichen Transportstrom von der Steuerung desselben zu trennen. In dieser Arbeit wird eine Dienstguteabbildungs- und -steuerungsarchitektur zur Ubertragung von multimedialen Daten uber heterogene Kommunikationssysteme vorgestellt und mit anderen Arbeiten verglichen. Des weiteren wird eine Implementierungsstrategie aufgezeigt, die es ermoglicht, das System in heterogenen Betriebssystem- und Kommunikationsun- gebungen einzusetzen.

An interactive multimedia distance learning system using distributed-object computing technology

Life-long learning is a major challenge for all companies, their employees and every other person interested in personal development. Distance learning and teletraining applications are strongly based on distributed multimedia information. In this paper an architecture of a scaleable corporate distance education system and the steps taken to guarantee different levels of quality of service (QoS) to the users are presented. The key components of the system are described in detail. The communication and middleware infrastructure as key elements of the architecture have to provide end-to-end quality of service support to the applications via application programming interfaces (APIs). Therefore, related architectural approaches and QoS-aware communication and middleware APIs are compared. Finally, a system architecture and the implementation status of the corporate distance learning and teletraining system are outlined.

Performance measurement in local and wide area ATM networks

Daimler-Benz Research and the International Computer Science Institute (ICSI) participated in one of the first transatlantic Asynchronous Transfer Mode (ATM) field trials. We describe the intention of the project Multimedia Applications on Intercontinental Highways (MAY), its infrastructure and results of various performance evaluations based on Classical IP over ATM (CLIP) and LAN Emulation (LANE). In addition the commonly used videoconferencing tool “vic” was evaluated in various measurements. We discuss the state of the art of wide area ATM networks and their limitations. Finally, solutions to some of the problems are outlined.

Multimediale Anwendungen in globalen ATM–Netzen

Die Daimler-Benz Forschung und das International Computer Science Institute (ICSI) nehnen am ersten interkontinentalen „Asynchroner Transfer Mode“ (ATM) Feldtest teil. Dieser Tagungsbericht gibt erste Erfahrungen mit multimedialen Anwendungen in globalen ATM-Netzen wieder. Insbesondere werden verschiedene Anwendungsszenarien und Ergebnisse von Performancemessungen diskutiert.

Evaluation of Mobility Management Approaches for IPv6 Based Mobile Car Networks1

Mobile information services are one of the key issues in the upcoming Information Society. Ubiquitous access to Internet has to be provided to mobile devices, such as intelligent cellular phones, personal digital assistants (PDAs) or mobile computers. In conjunction with the convergence of telecommunication networks towards the Internet Protocol (IP), mobility at network layer seems to be very promising. Most of the work done so far in this area considered mobile hosts rather than mobile networks. Future vehicular networks can be regarded as such moving IP based networks allowing seamless IP mobility for users and built-in devices while being attached to different access systems. In this paper existing mobility management approaches are evaluated with respect to their application for mobile networks and as a basis to develop new proposals. An outlook is given to the work that will be done in the EU IST project Over-DRiVE.

Architektur für eine integrierte Training Online Plattform

Im Rahmen der innerbetrieblichen Qualifikationsentwicklung kommen innerhalb der DaimlerChrysler AG verschiedene Lehrmethoden zum Einsatz. Neben den „klassischen“ Lehrmethoden sind momentan verstarkt Bemuhungen auf den Aufbau eines globalen Online-Lernsystems gerichtet. Die in diesem Rahmen in Entwicklung und Evaluation befindlichen Teilsysteme werden hier vorgestellt und die Motivation, die Ziele sowie die Ansatze zur Integration in ein Gesamtsystem beschrieben. Dieses System soll fur die verschiedenen Benutzerkategorien (wie z.B. Lernende, Ausbilder, Personalverantwortliche und Autoren) einen web-basierten Zugang zu den verschiedenen computer-bzw. web-basierten Lehrmethoden, sowie zu Kursangeboten und Lehrmaterialen bieten. Fur Ausbilder, Autoren und Personalverantwortliche sollen Schnittstellen zur Verwaltung, Pflege, und Komposition von Lehr- bzw. Kursangeboten und deren Medien, sowie zur Benutzer- und Ressourcenverwaltung angeboten werden. Das Gesamtsystem wird nicht als Software-Entwicklung im „traditionellen“ Sinne etabliert werden, sondern aus kommerziell verfugbaren Komponenten (sog. „Standardsoftware“) zusammengefugt werden. Die darauf zuruckzufuhrende Abweichung vom herkommlichen Lebenszyklus einer Eigenentwicklung wird ebenfalls dargestellt.