Timo Kosch

The scalability problem of vehicular ad hoc networks and how to solve it

Intervehicle communication (IVC) and its diverse application possibilities are experiencing growing interest both in research and industry. The dissemination of active safety messages generated by context-sensitive applications in vehicular ad hoc networks (VANETs) promises to improve passenger safety and comfort. One of the main challenges inherent to the deployment of VANETs is operability, both in very sparse and in highly overloaded networks. This scalability problem is not comprehensively addressed by existing approaches, as they only focus on parts of the problem. This article shows how a relevance-based, altruistic communication scheme helps realize scalability by optimizing the application benefit and the bandwidth usage. In-vehicle and intervehicle message selection are based on a relevance function that makes use of the current context and the content of the messages. A novel, proprietary cross-layer architecture and an IEEE 802.11e-based architecture can be used to implement the scheme

Communication architecture for cooperative systems in Europe

Wireless communications for intelligent transportation systems promise to be a key technology for avoiding the traffic nightmares of today - accidents and traffic jams. But there is one major challenge to be overcome before such a cooperative system can be put into place: standardization. This article provides an overview of the technical developments in Europe and their convergence toward a set of European standards. We address the current state of the standardization activities and the potential scenarios and use cases, and we describe the fundamental concepts of a European communication architecture for cooperative systems.

Strategies for Context-Adaptive Message Dissemination in Vehicular Ad Hoc Networks

In future deployments of vehicular ad hoc networks (VANETs) safety-related applications such as local danger warning (LDW) will use broadcast-based communication schemes to transmit information to other vehicles within the network. The unlimited flooding of a message throughout the whole network however, is neither feasible nor intended. The high resulting traffic load would congest the shared wireless medium and prevent other, potentially highly relevant and time-critical messages from getting access to the medium. Existing strategies to limit redundant packet retransmissions manage to make broadcast-based data packet dissemination more efficient and reliable. However, they do not take into account the individual networks nodes interest in information. In fact, the static mechanisms proposed are not adequate to leverage the limited network resources as efficiently as possible in varying network conditions and to transport information to where it is needed as fast as possible. Therefore, we propose an altruistic communication scheme which differentiates data traffic according to the benefit it is likely to provide to potential recipients. A system for calculating and leveraging message benefit and two different node architectures are presented. With the help of a comprehensive simulation environment, the performance of our concept is analyzed. Comparative simulative studies show that an improvement of the benefit provided to all the participants in a VANET is also possible with the help of the readily available IEEE 802.11e standard, but to a lower extent

A comparison of UMTS and LTE for vehicular safety communication at intersections

Vehicular safety communication promises to reduce accidents by assistance systems such as cross-traffic assistance. The information exchange is mostly foreseen to be handled via Dedicated Short Range Communication (DSRC). At intersections, DSRC reception is likely to be problematic due to Non-Line-Of-Sight reception conditions. Alternatively, the required information exchange could also be handled via cellular systems. While cellular systems provide potentially better coverage, they impose other performance constraints. This paper analyzes the suitability of UMTS and LTE for cross-traffic assistance as a worst case application in terms of load and latency demands. It investigates capacity and latency characteristics and discusses influence factors on performance as well as operational aspects. The focus is on the random access performance of the uplink channel. While cellular systems might have some advantages over DSRC, the study shows that UMTS will likely suffer from capacity limitations while LTE could perform reasonably well.

Vehicular safety communication at intersections: Buildings, Non-Line-Of-Sight and representative scenarios

Vehicular Dedicated Short Range Communication (DSRC) promises to reduce accidents by enabling assistance systems such as cross-traffic assistance. This application needs movement information from vehicles that are potentially in Non-Line-Of-Sight (NLOS) due to buildings at intersection corners. The amount of NLOS is determined by the placements of buildings. From another point of view, buildings influence the DSRC wireless channel by creating radio signal reflections and diffraction. Here, existing NLOS path-loss models for cellular communication with below roof-top base stations hint that the spatial placement of buildings has influence on the NLOS reception quality. This paper analyzes building positioning in the City of Munich with respect to DSRC. In a first step, it is investigated how much the line-of-sight is blocked by buildings. In a second step, the location of buildings is abstracted and the resulting data clustered to find a set of representative buildingposition scenarios. The presented scenario knowledge can be used in future research to configure meaningful simulations that investigate the radio channel at intersections under load and to select representative intersections for radio propagation field tests.

Self-organized and Context-Adaptive Information Diffusion in Vehicular Ad Hoc Networks

Vehicular ad hoc networks are considered as technology enabler for new automotive telematics services. In particular, those networks will enable foresighted active safety applications. However, in order to guarantee fast market introduction, a large variety of different applications with different traffic patterns must be supported. Due to the strict limitation of the available bandwidth in ad hoc networks, it is likely that in many situations the channel capacity is not sufficient to satisfy all transmission requests of all vehicles. However, a situation adaptive and self-organized utilization of the ad hoc network can optimize the overall utility of the deployed applications in the participating vehicles. Thereby, channel access is coordinated in a way that those data packets can access the channel first that provide the biggest expected utility for other vehicles in a specific situation. In this paper we delineate the effects of this implicit and situation adaptive information diffusion strategy and show that neither an explicit dissemination area or message life time is necessary.

Guest Editorial Vehicular Communications and Networks—Part II

Part I of this special issue is devoted to the physical layer, MAC layer, and physical-link cross-layer design technologies of vehicular communications and networks. There are 21 papers in this issue.

Topics in automotive networking

Presents an introduction to a special section which discusses issues related to energy savings as a leading application of vehicular communications, trust platform for vehicular networking, and intelligent transportation spaces.

Topics in Automotive Networking [Guest Editorial]

The two articles in this special series focus on automotive networking and address important topics related to the crucial physical layer.

Automotive Networking and Applications

The articles in this special section focus on automotive engineering networking and applications. In this 20th issue of the Automotive Networking and Applications Series, we are pleased to present two articles that address the following issues: distributed automotive security architecture based on blockchain (BC) and road traffic density estimation using mobile sensors such as smartphones. Vehicles are increasingly connected to the Internet, the roadside infrastructure, and other vehicles, thus enabling services in convenience, traffic efficiency, and driving safety. This connectivity, however, exposes vehicles to security and privacy threats such as remote hijacking of vehicles or location tracking of vehicle users, among others, while existing methods for security and privacy tend to experience challenges in terms of scalability and performance.