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Category: Mobile & Wireless Computing

Wireless Networks for Vehicular SupportPietro ManzoniTechnical University of Valencia, Spain

Carlos T. CalafateTechnical University of Valencia, Spain

Juan-Carlos CanoTechnical University of Valencia, Spain

Antonio SkarmetaUniversity of Murcia, Spain

Vittoria GianuzziUniversity of Genova, Italy

INTRODUCTION

Vehicular Ad hoc NETworks (VANETs) is an area under intensive research that promises to improve security on the road by developing an intelligent transport system (ITS). The main purpose is to create an inter-communication network among vehicles, as well as between vehicles and the supporting infrastructure. The system pretends to offer drivers data concerning other nearby vehicles, especially those within sight.

The problem of information sharing among vehicles and between the vehicle and the infrastructure is another critical aspect. A general communication infrastructure is required for the notification, storage, management, and provision of context-aware information about user travel. Ideally an integrated vehicle-to-vehicle (V2V) and vehicle-to-infra-structure (V2I) communication paradigm enriched with an information management system would solve the problem. The infrastructure should manage all the collected safety events garnered from vehicles and the interesting informa-tion to be provided to the user, which is adapted to the car context and driver preferences.

Finally, security issues should be considered. Since the information conveyed over a vehicular network may affect critical decisions, fail-safe security is a necessity. The first directive for any V2V communication scheme is, therefore, that every safety message must be authenticated. Because of the high speed and therefore short duration within which communication between two cars is possible, communica-tion must be non-interactive, and message overhead must be very low. The urgency of safety messages implies that authentication must be instantaneous without additional communication.

Moreover, providing strong security in vehicular net-works raises important privacy concerns that must also be considered. Safety messages include data that is dangerous to the personal privacy of vehicle owners. Most relevant is the danger of tracking a vehicle through positional infor-mation. A set of security basics to address these challenges should be proposed that can be used as the building blocks of secure applications.

In this article we will focus on the aforementioned tech-nologies and engineering issues related to vehicular ad-hoc networks, emphasizing the challenges that must be overcome to accomplish the desired vehicular safety infrastructure.

BACKGROUND

Ubiquitous computing is nowadays an emerging research field in mobile communications, due to more and more integration of heterogeneous services over different operation environ-ments. The capacity of customizing services to the client, and the adaptation of its behavior according to the context, will offer the user value-added features in the new age of computer communications. Taking into account this premise, in this article our aim is to create a feasible environment for providing integrated services in the vehicle field.

Wireless communications in the vehicle field through ad hoc networks (or Vehicular Ad hoc NETworks–VANETs) are currently being used as a novel and promising technol-ogy to improve driving safety. Mainstream research usually considers these communication patterns to offer intelligent transportation systems (ITSs), where one of the most im-portant aims is the creation of communication networks among vehicles, in vehicle-to-vehicle transmissions (V2V),

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but without forgetting communications between vehicle and infrastructure (V2I). The usefulness of these developments is focused on providing every vehicle with information about the surrounding vehicles, and especially the ones not located in the field of vision.

Due to the continuous improvements of communica-tion technologies, a great number of considerations must be taken into account when a network system is elected. Although VANET developments have predominated in V2V communications, it is necessary to study whether the facili-ties offered by the network design cover the requirements collected from the future deployable services. Collision avoidance applications have been the main safety service implemented for the vehicle field. However, a great number of non-safety services are appearing. When the amount of services for the vehicle side grows, more consideration is needed. It is mandatory to research in technological solutions which deal with the requirements of a generic and flexible architecture for service provisioning and usage.

For a correct design of such systems, it is necessary to take into account the vehicular environment. Here, high-speed mobility and special movement patterns can be found, where the creation and breakage of links between nodes appear continuously. The presence of an excessive or null rate of equipped vehicles is another important factor which must be considered. This fact and the need for reliable end-to-end communication make the design of a vehicular communica-tion system a complex task.

The main objective of any project in this area is to offer an integrated solution for the deployment of an ITS using the VANET communication technology overall. The schema considered can be seen in Figure 1. The system should ap-ply techniques inside the field of ubiquitous computing in the vehicle field, where numerous programmatic devices can interact with the user in a transparent way. This way, the system should have enough intelligence to analyze the context and efficiently detect hazardous and emergency situations, generate driver warnings in critical cases, and interact with the infrastructure when a global knowledge can be useful.

A CROSS-LAYER APPROACH TO VANET DESIGN

The design of a complete VANET solution must cover differ-ent technological areas, and several disciplines are involved in the development of such a system. In the following we will outline all the interrelated layers that must work together to provide a comprehensive architecture.

Modeling, Evaluation, and Simulation

In classical MANETs, researchers often use a typical set of simulation parameters. These parameters are inadequate for

Figure 1. Overall scheme of the proposed architecture

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many MANETs, and particularly for VANETs. The MANET research community is aware of resulting limitation because of the simplification of some hypotheses (Kotz et al., 2004). In the VANET context, different researching groups are working to improve models in order to perform experiments close to reality. For example, Wu, Fujimoto, Guensler, and Hunter (2004) use their own simulator, called CORSIM, for creating mobility traces for other simulators. In the same way, Choffnes and Bustamante (2005) use a new mobility model called STRAW for modeling real traffic patterns. This model has an easy car persecution model and the chance of controlling the traffic to create congestion situations.

On-Board and Roadside Equipment

Current studies about technologies for on-board equipment are directed to the hardware that is needed to incorporate into the vehicle in order to offer one or several services with certain functionality (Skarmeta et al., 2002; Massaki, Xuchu, Hideki, Mami, & Masaki, 2004). An important issue will be the implementation of a positioning system with a high degree of reliability. Also we will pay special attention to the computer considered in the on-board unit. At the start there was a tendency to employ specific-purpose computers. Nevertheless, the development of several services advises the employment of general purpose computers (Simonds, 2003; Santa, 2007). This computer must be fitted with the

communication interfaces needed to connect to the commu-nication system that will be proposed in the project. In the car environment, although having used many communica-tion technologies (Nolte, Hansson, & Lo Bello, 2005), the most interesting ones are the 802.11 and cellular networks. 802.11 networks have usually been considered in VANET networks and allow the deployment of cooperative services among vehicles. Nevertheless, new solutions were developed for communicating with the infrastructure (Okabe, Shizuno, & Kitamura 2005). On the other hand, UMTS is the most appropriate cellular technology for the vehicular environ-ment. Usually, connections through the cellular network are being directed to infrastructure communications. However, in the project development, a V2V and V2I communication architecture based on cellular networks will be proposed.

A V2I communication infrastructure will need roadside support. Although in cellular networks operators offer hard-ware deployment, the research in new V2I communication technologies must take into account several technological considerations of the road infrastructure.

Horizontal and Vertical Handoffs Between Communication Systems

The interest in offering Internet access in heterogeneous scenarios and on mobile platforms like trains, buses, or airplanes has caused the creation of the NEtwork MObility

Figure 2. A VANET system vertical architecture

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Working Group (NEMO) of the IETF (Internet Engineering Task Force). This group is in charge of defining mechanisms for managing network mobility as a whole, allowing network handoffs between different physical systems, but maintain-ing the same logical connection over IP (Internet Protocol). NEMO objectives are becoming real due to the improvement of cellular networks and the integration of WLAN technolo-gies like WAVE (IEEE 802.11p, or Wireless Access in the Vehicular Environment) or CALM (Continuous Air interface for Long and Medium distance).

An important objective resides in offering mobile nodes an efficient and scalable mechanism for changing their network attachments, keeping their IP address, and keeping alive all the high-level connections (Yabusaki, Okagawa, & Imai 2005). In this way there are some interesting works, like MIPv6 and Hierarchical Mobile IPv6 (HMIPv6) (Yan & Atwood, 2006), with the aim of improving mobile com-munications in certain circumstances, making the handoff a secure and efficient process.

Security in Data Networks

Being able to protect members of possible security attacks is essential in this kind of network, without eliminating the possibility of giving context services. Attacks can be classi-fied into passive attacks and active attacks. Passive attacks consist of “listening” to the information that is transmitted in the network, without directly affecting to the network operation (Yanchao, Wei, & Wenjing, 2005). Generally, hackers enter with the aim of examining the general state and the network traffic. This analysis can be made with the objective of damaging the network availability or traffic. The privacy about position is a special type of information confidentiality, which is defined as the possibility of stop-ping third parties from knowing the current or a previous vehicle position.

Active attacks (Liu, Fu, Xiao, & Lu, 2007) imply a bigger attacker interaction with the network, by means of devices manipulation, “man-in-the-middle” techniques, or denial-of-service strategies. To solve these problems it is necessary to use cryptography-based techniques, which allow authenti-cating both the transmitted information and the sender, for example by means of digital signatures and hash functions. The aim is providing VANET vehicles with classic services of authentication, non-repudiation of origin, and information integrity, as well as specific for VANET networks. Due to the high speed of movement, techniques for detection of so-called “false alarms,” which are produced by information delays or alarms repetition, must been researched. In moni-toring systems where an information management station for vehicles is situated at the infrastructure, security issues for information transmissions are also an important fact to be considered (Hoh, Gruteser, Xiong, & Alrabady, 2006).

Vehicle to Infrastructure Communications and Alternatives to VANET

Though VANET networks are the main research point in vehicular networks, there are situations where current developments can limit the use of some services. When the distance between two transmitting vehicles increases considerably, a communication based on VANET can pres-ent poor performance. On the other hand an interconnection with a fixed network requires efforts that can not be scalable in cost. With this meaning, the project will direct an effort in finding other alternatives that complement the VANET communication system.

Some authors have noticed VANET cadences and the usefulness of P2P (peer-to-peer) networks to create an ar-chitecture that allows cooperative work between vehicles (Rybicki et al., 2007) or a connection with the infrastructure (Baresi et al., 2005), this way avoiding VANET network restrictions. By means of a P2P network, nodes can use in a transparent mode an underlying network infrastructure and work cooperatively using a logical interconnection mesh. Vehicles can take advance of this system and communicate with its environment through several services in a V2V or V2I pattern. However, an underlying technology is necessary to “physically” connect the vehicle to the network.

Cellular networks were especially important in con-necting with the infrastructure. Previous connection rates, of approximately 300kps, have been overcome by HSPA technology, which already offers significant improvements in delay and bandwidth to start considering UMTS as an appropriated technology for vehicular networks. For this reason, the project will cover issues regarding the use of cellular networks in vehicles and will consider an alternative network system for V2V and V2I communications based on P2P over UMTS.

FUTURE TRENDS

Vehicular networks introduce a new complex environment for communication engineers. The communication channel varies from a simple point-to-point microwave link for cars in open areas, to rich Rayleigh fading within the cities. Also the channel varies considerably every few seconds and the blockage of line of sight can occur frequently. Adaptive and efficient channel estimation algorithms must be found, diversity techniques to overcome fading effects should be examined, and Doppler effects should be carefully considered. The link layer is expected to provide a varying delay and different QoS classes to satisfy the different requirements of the applications.

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WTechniques of service provision which make use of

vehicle position are the so-called location-based services (LBSs). The traffic environment and the information that vehicles receive require a more complete modeling about the destination of the user and his or her preferences in order to reach the so-called context-based services. The subscription strategy is of special interest, talking about a generic service provision system. Typical Internet services, like Web naviga-tion, transactions management, bookings, and so forth, use a client/server strategy where the server replies to a previous client request, and operation requisites of vehicular services respond to other, more suitable communications strategies, known as publish/subscribe. Using this methodology, the user does not have to send an explicit request to the system to receive certain information, but neither would receive continually non-desired information, as happens with the vehicular RDS (radio data system). In a publish/subscribe scheme, the user manifests his or her interest about receiving certain information, and the system is in charge of sending pertinent notifications (Cugola & Jacobsen 2002). This way, a publish/subscribe system perfectly operates not only with a context-aware service provision, but also with users’ requirements modeling.

The Ontology Web Language (OWL) and the adaptation of Web content by means of captive portals will be combined in this project with the service subscription strategy in or-der to present a ubiquitous environment of services for the driver. The usefulness of OWL has been proven in different environments, including aiding systems for museum visits (Chou, Hsieh, Gandon, & Sadeh 2005). These applications model the museum environment and adapt the information to the user according to his or her movement throughout the facilities. The adaptation of this idea to a vehicular environ-ment is considered of special interest (Santa, 2007).

CONCLUSION

In this article, we presented the VANET research area, a very active area that is expected to truly enhance car drivers’ lives. The main focus is security, but also infotainment (the combination of information and entertainment) is of interest, especially from the economic point of view.

We described the areas where most of the research activ-ity is focusing and evidenced that a transversal solution is crucial for this type of network.

Fast and reliable dissemination of alerts on accidents or other road hazards is a critical application of vehicular networks. A protocol that supports the dissemination of emergency messages should ensure the timely delivery of such messages to all the vehicles passing through the poten-tially affected region during the lifetime of an emergency. This protocol might exploit a hybrid, cluster-based vehicular

network architecture, where the bulk of communication between vehicles takes place over ad hoc networks for improved scalability and efficiency. Cellular communica-tion can also be used to improve reliability when network partitions hinder the message delivery.

REFERENCES

Baresi, L., Ghezzi, C., Miele, A., Miraz, M., Naggi, A., & Pacifici, F. (2005). Hybrid service-oriented architectures: A case-study in the automotive domain. Proceedings of the 5th International Workshop on Software Engineering and Middleware (SEM’05) (pp. 62-68).

Choffnes, D.R., & Bustamante, F.E. (2005). An integrated mobility and traffic model for vehicular wireless networks. Proceedings of ACM VANET.

Chou, S., Hsieh, W., Gandon, F.L., & Sadeh, N.M. (2005). Semantic Web technologies for context-aware museum tour guide applications. Proceedings of the 19th International Conference on Advanced Information Networking and Ap-plications, Washington.

Cugola, G., & Jacobsen, H. (2002). Using publish/subscribe middleware for mobile systems. ACM SIGMOBILE Mobile Computing and Communications Review, 6(4), 25-33.

Hoh, B., Gruteser, M., Xiong, H., & Alrabady, A. (2006). Enhancing security and privacy in traffic-monitoring systems. IEEE Pervasive Computing, 5(4), 38-46.

Kotz, D., Newport, C., Gray, R.S., Liu, J., Yuan, Y., & Adid Elliott, C. (2004). Experimental evaluation of wireless simu-lation assumptions. Proceedings of ACM MSWIM.

Liu, J., Fu, F., Xiao, J., & Lu, Y. (2007, July 30-August 1). Secure routing for mobile ad hoc networks. Proceedings of the 8th ACIS International Conference on Software Engineering, Artificial Intelligence, Networking, and Parallel/Distributed Computing (SNPD 2007) (vol. 3, pp. 314-318).

Massaki, W., Xuchu, M., Hideki, H., Mami, M., & Masaki, S. (2004). iCAN: Pursuing technology for near-future ITS. IEEE Intelligent Systems, (January/February), 18-23.

Nolte, T., Hansson, H., & Lo Bello, L. (2005, July). Wireless automotive communications. Proceedings of the Euromicro Conference on Real-Time Systems (ECTRS’05), Palma de Mayorca, Spain.

Okabe, T., Shizuno, T., & Kitamura, T. (2005, June). Wireless LAN access network system for moving vehicles. Proceed-ings of the 10th IEEE Symposium on Computers and Com-munications (ISCC05), La Manga del Mar Menor, Spain.

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Rybicki, J., Scheuermann, B., Kiess, W., Lochert, C., Fal-lahi, P., & Mauve, M. (2007, September 9-14). Challenge: Peers on wheelsa road to new traffic information systems. Proceedings of the 13th Annual ACM International Confer-ence on Mobile Computing and Networking (MobiCom ’07) (pp. 215-221), Montréal, Canada.

Santa, J., Muñoz, A., & Skarmeta, A.F.G. (2007). A con-text-aware solution for personalized en-route information through a P2P agent-based architecture. Proceedings of the 2007 International Conference on Computational Science and Its Applications (ICCSA 2007) (pp. 710-723). Berlin: Springer-Verlag (LNCS 4707).

Santa, J., Ubeda, B., & Skarmeta, A.F.G. (2007, January). A multiplatform OSGi based architecture for developing road vehicle services. Proceedings of the Consumer Com-munications & Networking Conference 2007 (CCNC 2007), Las Vegas, NV.

Simonds, C. (2003). Software for the next-generation auto-mobile. IT Professional, (November/December), 7-11.

Skarmeta, A.F.G., Barbera, H.M., Izquierdo, M.Z., Minaro, B.U., de Leon, F.C.G., & Balibrea, L.M.T. (2002). MIMICS: Exploiting satellite technology for an autonomous convoy. IEEE Intelligent Systems, 17(IV/V), 85-89.

Wu, H., Fujimoto, R., Guensler, R., & Hunter, M. (2004). MDDV: A mobility centric data dissemination algorithm for vehicular networks. Proceedings of ACM VANET.

Yabusaki, M., Okagawa, T., & Imai, K. (2005). Mobility management in All-IP mobile network: End-to-end intel-ligence or network intelligence? IEEE Communications Magazine, 43(12).

Yan, C., & Atwood, J.W. (2006). Towards minimizing service degradation during MIPv6 handovers. Proceedings of the 31st IEEE Conference on Local Computer Networks (pp. 549-553).

Yanchao, Z., Wei, L., & Wenjing, L. (2005). Anonymous communications in mobile ad hoc networks. Proceedings

of the 24th Annual Joint Conference of the IEEE Computer and Communications Societies (vol. 3, pp. 1940-1951).

KEY TERMS

Global Navigation Satellite System (GNSS): A satellite system that is used to pinpoint the geographic location of a user’s receiver anywhere in the world.

Mobile Ad-hoc NETwork (MANET): A type of wire-less network, made of a self-configuring network of mobile devices. These devices are connected by wireless links. The union of all these devices forms an arbitrary topology.

On-Board Unit (OBU): Computing device located in a vehicle that establishes the connection with the RSU and the other OBUs on nearby vehicles.

Roadside Unit (RSU): Computing device located on the roadside that provides connectivity support to passing vehicles.

Universal Mobile Telecommunications Service (UMYS): A third-generation (3G) broadband, packet-based transmission of text, digitized voice, video, and multimedia at data rates up to 2 Mbps.

Vehicle to Infrastructure (V2I): Involves all the com-munication aspects between vehicles and the supporting infrastructure.

Vehicle to Vehicle (V2V): Relates all the data com-munication that takes place between various vehicles on the road.

Vehicular Ad hoc NETwork (VANET): A mobile network whose node are vehicles (i.e., car, trucks, etc.); considered an extension of a MANET (Mobile Ad hoc Networks) because of the possibility of working without a fixed infrastructure.