Vehicular Ad Hoc NetworksHannes Hartenstein, University of Karlsruhe, Germany Ken Laberteaux, Toyota Technical Center Ann Arbor, USA
Vehicular ad hoc networks (VANETs) can help to increase safety and comfort ‘on the road’. As an element for active, i.e., preventive safety, these VANETs can efficiently warn and inform drivers via direct wireless intervehicle communications. Thereby, the range of awareness of a driver is extended from current line-of-sight to the radio range of a wireless transceiver. With multi-hop communication, each vehicle can benefit from the locally sensed data of surrounding vehicles or from multi-hop access opportunities. Clearly, sensing, disseminating and retrieving information on the current surrounding shows a potential for improving transport efficiency and comfort. Recently, the promises of wireless communications to support vehicular safety applications have led to several national/international projects around the world: DSRC, VSC, VII in USA, C2CCC in Europe, AVS in Japan or Network on Wheels in Germany, to name a few. All these efforts have as a main goal to improve safety in vehicular environments by the use of wireless communications, but also consider transport efficiency, comfort and environment. In comparison to other communication networks VANETs have unique requirements with respect to applications, types of communication, self-organization and security. In the context just described, the proposed tutorial has two main goals:
- To present a detailed description of the state of the art of VANETs pointing to research, projects and standardization efforts that have been done.
- To outline the challenges of the current technologies and to discuss open issues and directions of further research in this field.
1. Motivation: Applications and Recent projects (0.5 hours)
First, we motivate the need for wireless communications in vehicular environments. We describe the different types of applications that are being considered for VANETs. The spectrum ranges from active safety or safety of life applications to traffic information, music/maps download and multi-hop internet connection. We address different requirements associated to specific applications, e.g., robustness with respect to false alarms, sensor accuracy, the impact on driving behavior or required penetration rates. Second, an overview on recent project and standardization activities in the field of VANETs is provided including VII, VSC, CAMP, C2CCC, COMeSafety, NoW and others.
2. Mobility and Radio Channel incl. Modeling and Simulations (0.5 hours)
- Network topology: vehicular traffic characteristics. This section covers measurements from vehicular traffic on highways and in cities and associated models (like Wiedemann as well as Schreckenberg-Nagel models) and simulation tools that couple/combine vehicular traffic and network simulation.
- Radio propagation in vehicular environments. This section covers measurements and discusses various models including the standard two-ray ground model and more realistic models for fast fading like the m-distribution of Nakagami. We point out the relevance of using the probability of reception as the figure of merit.
3. Communication Technology and Strategies incl. Modeling and Simulations (1.0 hours)
- IEEE 802.11p standard. Starting from IEEE 802.11a, the ‘p-standard’ will provide the required robustness for VANET communiations. We present the key design aspects and outline a ‘p-compliant’ simulation model. In addition, we outline recent receiver structures.
- Forwarding, routing, and information dissemination strategies. We discuss various forwarding strategies focussing on position-based techniques including ‘contention-based forwarding’. We survey various ‘intelligent flooding’ and information dissemination approaches. Scenarios for highways and cities are taken as example.
- Challenges of robust inter-vehicle communications. We will point
out the challenges depending on the different types of potential
applications. Mainly the following types of communications and
applications will be addressed:
- active safety: periodic broadcast messages,
- emergency warning: event driven messages, information dissemination, and
- non-safety applications: point-to-point communications, routing/forwarding strategies.
4. Architectural and application-specific issues (0.5 hour)
We discuss the relationship to sensor networks and peer-to-peer networks. In addition, decision and control aspects for various VANET-specific applications are addressed. Based on the interdependencies between ‘layers’ we discuss alternative protocol architectures for VANETs. Furthermore, we survey middleware approaches that have been proposed for vehicle-to-vehicle and vehicle-to-roadside communications.
5. Security, privacy and incentives aspects (0.5 hour)
Security is a crucial aspect in VANETs in order to become a reliable and accepted system bringing safety on public roads. In this section we will discuss the major security goals (authenticity, message integrity and source authentication, privacy, and robustness) and proposals in the context of VANETs. Finally, we will describe the requirements and strategies being considered to bring the technology to the market. Aspects such as costs or the willingness of consumers to pay for the technology will be addressed as well as different wireless technologies seen as competitors in the market introduction phase.
6. Discussion (0.5 hours)
Audience and Prerequisite Knowledge
A basic understanding of IEEE 802.11 and of ad hoc networks in general is beneficial but not required. There exists a broad range of potential participants who will be interested in this emerging topic. We identify two main profiles:
- Researchers from both industry (e.g., automotive, telecommunications, hardware) and academia that are involved (or would like to be) in inter-vehicle communications and want to know the state of the art (w.r.t. models, protocols and tools), challenges and directions of further research in this field.
- Industry representatives that see in VANETs a new field for their business for their companies (e.g., service providers, telecom operators, toll collect system providers) and want to understand the possibilities and state of the art of such technology.
Biographies of Presenters
Hannes Hartenstein is a professor at the University of Karlsruhe, Germany with affiliations to the Institute of Telematics and the university’s Computing Center. He is also member of the scientific directorate of IBFI Schloss Dagstuhl. Before joining University of Karlsruhe in 2003 he was with NEC Europe Ltd., Network Labs in Heidelberg, Germany. He was NEC’s project leader (2001-2003) for the ‘FleetNet – Internet on the Road’ project partly funded by the German Ministry of Education and Research (BMBF). In the FleetNet project, DaimlerChrysler together with NEC, Siemens, Bosch and others pioneered and explored the feasibility of vehicular ad hoc networks. Hannes is now involved in the ‘NOW: Network on Wheels’ project, again partly funded by the German BMBF. In the NOW project, DaimlerChrysler, Volkswagen and BMW teamed up to push the development of VANET technology. Hannes was general co-chair of the 2nd ACM International Workshop on Vehicular Ad Hoc Networks that was held in conjunction with ACM Mobicom in Cologne, Germany, September 2005. He was program co-chair of the ACM VANET workshop in 2006. He co-authored more than 80 publications, about 25 devoted to vehicular ad hoc networks. For further information please see http://dsn.tm.uni-karlsruhe.de.
Ken Laberteaux is a Senior Principal Research Engineer for the Toyota Technical Center in Ann Arbor, MI. Ken’s research focus is information-rich vehicular safety systems, focusing on architecture and protocol design for vehicle-to-vehicle and vehicle-to-roadside wireless communication. He is one of the founders and two-year (2004, 2005) General Co-Chair of the highly-selective, international Vehicular Adhoc Networks (VANET) workshop. Ken serves as the technical lead for communications of the multi-year, multi-million dollar Vehicle Safety Communications-Applications collaboration project between the US Government and several automotive companies. He also serves as Toyota’s technical lead for various ITS standards efforts and multi-company demonstration projects. Before joining Toyota, Ken spent ten years as a researcher at the Tellabs Research Center, a leading North American telecommunications lab. While working full-time at Tellabs, Ken earned his M.S. (1996) and Ph.D. (2000) degrees in Electrical Engineering from the University of Notre Dame, focusing on adaptive control for communications. In 1992, he received his B.S.E. (summa cum laude) in Electrical Engineering from the University of Michigan, Ann Arbor.