Dipl.-Inf.

Roscher, Karsten

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On the feasibility of multi-hop communication in a realistic city scenario

2017 , Roscher, Karsten

Vehicular ad hoc networks (VANETs) are about to enter the market in the upcoming years. While direct message exchange is limited to a few hundred meters and mostly line-of sight, multi-hop forwarding can significantly extend the communication range. In this paper, the influence of network density and vehicle distribution on multi-hop communication in VANETs is investigated using a model of the city of Luxembourg. Introducing an idealistic reference routing we identify the need for high penetration rates to achieve acceptable reliability independent of the selected routing protocol. A comparison with Greedy forwarding shows its weaknesses to select proper next hop candidates when the number of equipped vehicles increases.

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Simulationsbasierte Evaluierung eines zeit- und ortsbasierten Pseudonym-Wechsel-Verfahrens für ETSI ITS

2015 , Bittl, Sebastian , Schlegel, Marius , Roscher, Karsten

Die Einführung drahtloser Car-to-X-Kommunikation eröffnet zahlreiche Möglichkeiten für die Realisierung zukünftiger Fahrerassistenzsysteme. Aufgrund einer Vielzahl an verkehrssicherheitskritischen Anwendungsfällen werden in bisherigen Standards zur Wahrung von Authentizität, Integrität und Verbindlichkeit digitale Zertifikate und digital signierte Nachrichten verwendet. Um die Privatsphäre der Fahrzeugnutzer zu gewährleisten, setzt das bisher standardisierte Konzept auf ein unkoordiniertes Austauschen der Teilnehmeridentitäten bzw. ihrer Zertifikate. Da zahlreiche Schwächen in diesem Konzept identifiziert wurden, führen fortgeschrittene Ansätze zeitlich synchronisierte Identitätswechsel aus. Diese erfordern jedoch im Regelfall zusätzlichen Kommunikationsaufwand und limitieren die Erfolgsrate des Angreifers nur eingeschränkt. In dieser Arbeit wird daher ein zeit- und ortsabhängiges Verfahren vorgestellt, mit dem der erzielbare Lernfortschritt beim Tracking durch einen Angreifer minimiert wird, ohne eine zusätzliche Kommunikation der Teilnehmer untereinander zu erfordern. Die simulationsbasierte Evaluierung bestätigt die gute Verwendbarkeit des Ansatzes.

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Protocol modeling accuracy in VANET simulators

2017 , Bittl, Sebastian , Roscher, Karsten

Vehicular ad hoc networks are about to enter the mass market in upcoming years. High effort for real world field tests leads to high dependency of development and evaluation of such networks on simulations. We compare supported features of common simulation frameworks with current standards and study the performance impact of incomplete standard conformance. We find that a lack of support for data encoding schemes and security functionality may massively affect simulation results. Our findings apply to many well-known simulation frameworks. Proposals to overcome identified weaknesses are provided.

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Forwarding in VANETs: GeoNetworking

2015 , Tomatis, Andrea , Menouar, Hamid , Roscher, Karsten

Nowadays connectivity in the vehicles is becoming the base to enable safety, traffic efficiency, and infotainment applications. These applications require to exchange information with specific geographical locations. After a decade of research and standardization activities, a dedicated technology to support forwarding in Vehicular Ad-hoc Network (VANET) called GeoNetworking has been completed in Europe. This chapter will provide an overview of GeoNetworking features and functionalities describing geographical addressing and geographical forwarding in an easy and understandable way for both technical and non-technical readers.

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Efficient distribution of certificate chains in VANETs

2017 , Bittl, Sebastian , Roscher, Karsten

Wireless car-to-X communication technology is about to enter the mass market within the next years. Thereby, security in created vehicular ad-hoc networks depends on digital signatures managed by a multi-level certificate hierarchy. Certificate distribution is critical in regard to channel usage and delay of data reception via security caused packet loss. These issues are even more significant in case not only pseudonym certificates, but also certificate authority certificates, have to be exchanged between nodes on demand. Prior work has not treated dissemination of higher level elements from a multi-level certificate chain in detail. Thus, this work provides a study on the recently standardized algorithms. Several drawbacks of the straight forward solution taken so far are identified, which include severe denial of service weaknesses. Solutions to the distribution problem are found to be similar to the ones of the packet forwarding problem encountered in position-based routing. Hence, we study several algorithms for efficient distribution of a certificate chain in regard to channel load, which are adapted from their counterparts in position-based routing. Thereby, a combination of pseudonym certificate buffering with requester based responder selection is found to be able to completely remove the requirement for certificate chain distribution in VANETs. The introduced design avoids the found denial of service weakness, while decreasing the worst case size of the security envelope of VANET messages by more than a third at the same time.

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A position-based routing module for simulation of VANETs in NS-3

2012 , Katsaros, Konstantinos , Dianati, Mehrdad , Roscher, Karsten

Geonetworking and the corresponding routing protocols play an important role in application of Vehicular Ad-hoc Networks (VANETs). This paper presents the architecture and implementation of CLWPR (Cross-Layer, Weighted, Position-based Routing), a position-based routing protocol optimized for VANETs in NS-3 simulation environment. It utilizes mobility information from nodes and cross-layer information from PHY and MAC layer in order to increase its efficiency and reliability, respectively. More specifically, we present the changes that have been introduced to facilitate geonetworking, as well as the carry-n-forward mechanism. In addition, we developed a basic navigation facility that can provide information about the road and distance between two nodes.

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