Vehicular networks are likely to become the most relevant form of mobile ad hoc networks. In this paper, we address the security of these networks. We provide a detailed threat analysis and devise an appropriate security architecture. We also describe some major design decisions still to be made, which in some cases have more than mere technical implications. We provide a set of security protocols, we show that they protect privacy and we analyze their robustness, and we carry out a quantitative assessment of the proposed solution.

Multihop data delivery through vehicular ad hoc networks is complicated by the fact that vehicular networks are highly mobile and frequently disconnected. To address this issue, we adopt the idea of carry and forward, where a moving vehicle carries a packet until a new vehicle moves into its vicinity and forwards the packet. Being different from existing carry and forward solutions, we make use of predictable vehicle mobility, which is limited by traffic pattern and road layout. Based on the existing traffic pattern, a vehicle can find the next road to forward the packet to reduce the delay. We propose several vehicle-assisted data delivery (VADD) protocols to forward the packet to the best road with the lowest data-delivery delay. Experimental results show that the proposed VADD protocols outperform existing solutions in terms of packet-delivery ratio, data packet delay, and protocol overhead. Among the proposed VADD protocols, the Hybrid Probe (H-VADD) protocol has a much better performance.

In this paper we conduct a feasibility study of delay-critical safety applications over vehicular ad hoc networks based on the emerging dedicated short range communications (DSRC) standard. In particular, we quantify the bit error rate, throughput and latency associated with vehicle collision avoidance applications running on top of mobile ad hoc networks employing the physical and MAC layers of DSRC. Towards this objective, the study goes through two phases. First, we conduct a detailed simulation study of the DSRC physical layer in order to judge the link bit error rate performance under a wide variety of vehicles speeds and multi-path delay spreads. We observe that the physical layer is highly immune to large delay spreads that might arise in the highway environment whereas performance degrades considerably at high speeds in a multi-path environment. Second, we develop a simulation testbed for a DSRC vehicular ad hoc network executing vehicle collision avoidance applications in an attempt to gauge the level of support the DSRC standard provides for this type of applications. Initial results reveal that DSRC achieves promising latency performance, yet, the throughput performance needs further improvement.

The emergence of the 802.11a-based Dedicated Short Range Communications (DSRC) standard and advances in mobile ad hoc networking create ample opportunity for supporting delay-critical vehicular safety applications in a secure, resource-efficient, and reliable manner. In this paper, we focus on the suitability of DSRC for a class of vehicular safety applications called Cooperative Collision Warning (CCW), where vehicles periodically broadcast short messages for the purposes of driver situational awareness and warning. First, we present latency and success probability results of Forward Collision Warning (FCW) applications over DSRC. Second, we explore two design issues that are highly relevant to CCW applications, namely performance trends with distance and potential avenues for broadcast enhancements. Simulation results reveal interesting insights and trade-offs related to application-perceived latency and packet success probability performance. For instance, we conjecture the existence of an optimal broadcast rate that minimizes our novel latency measure for safety applications, and we characterize it for plausible scenarios.

Vehicular ad hoc networks (VANETs) are envisioned to provide us with numerous interesting services in the near future. One of the most promising applications is the dissemination of commercial advertisements via car-to-car communication. However, due to non-cooperative behavior of selfish nodes or even malicious ones in the real-world scenario, such vehicular advertisement system cannot be realized unless proper incentives and security mechanisms are taken into consideration. This paper presents Signature-Seeking Drive (SSD), a secure incentive framework for commercial ad dissemination in VANETs. Unlike currently proposed incentive systems, SSD does not rely on tamper-proof hardware or game theoretic approaches, but leverages a PKI (Public Key Infrastructure) to provide secure incentives for cooperative nodes. With a set of ad dissemination designs proposed, we demonstrate that our SSD is robust in both incentive and security perspectives.

Abstract—Vehicular ad hoc networks (VANETs) have recently received considerable attention. To support VANET-based applications, it is important to disseminate data from an information source (data center) to many vehicles on the road. Although disseminating data from a server to a large number of clients has been studied in the database community and the network community, many unique characteristics of the VANET bring out new research challenges. In this paper, we propose a data pouring (DP) and buffering paradigm to address the data dissemination problem in a VANET. In DP, data are periodically broadcast to vehicles on the road. In DP with intersection buffering (DP-IB), data poured from the source are buffered and rebroadcast at the intersections. We provide analytical models to explore the dissemination capacity (DC) of the proposed schemes. The analytical models also provide guidelines on choosing the system parameters to maximize the DC under different delivery ratio requirements. Simulation results show that the proposed DP-IB scheme can significantly improve the data delivery ratio and reduce network traffic. Index Terms—Ad hoc networks, broadcasting, data dissemination, dissemination capacity, vehicular networks. I.

Successes and failures during rescue operations after hurricane Katrina and the Twin Towers attack demonstrated the importance of supporting first responders with adequate means to perform their operations in an effective and safe way. From a networking point of view, one of the main challenges is that of providing first responders with multimedia information about the emergency as soon as possible, even from a remote location. To this aim, we designed an inter-vehicular communication system able to quickly discover and transmit real time multimedia information from around a crisis area to approaching first responders ’ vehicles. As vehicular communications are highly variable in nature, we endowed our system with a transmission range estimator that is put to good use to reduce the number of hops that a video triggering message sent by a vehicle will experience to reach its destination. Experimental results demonstrate the efficacy of our scheme in reducing the message delivery time and the traffic generated. 1.

Abstract — As the technology available on cars is increasing, a wide range of applications, from safety to entertainment, are becoming factually accessible to passengers. Many of these applications involves a one-to-many transmission model where a single car broadcasts a message that has to be forwarded, even with multiple hops, in a very short time to all the other cars located within a range of few kilometers from the source. Since the high mobility and density of a car network scenario, specific solutions need to be devised to choreograph a fast-delivery multihop broadcast. To this aim, we developed a practical and efficient technique that allows cars to estimate their communication range with the help of a very limited message exchange and exploit this information to reduce the number of transmissions, as well as the hops to be traversed, and hence the time, required by a broadcasted message to reach all the cars following the sender within a certain distance.

Abstract — This paper considers the problem of coordinating multiple vehicles with kinodynamic constraints that operate in the same partially-known environment. The vehicles are able to communicate within limited range. Their objective is to avoid collisions between them and with the obstacles, while the vehicles move towards their goals. An important issue of real-time planning for systems with bounded acceleration is that inevitable collision states must also be avoided. The focus of this paper is to guarantee safety despite the dynamic constraints with a decentralized motion planning technique that employs only local information. We propose a coordination framework that allows vehicles to generate and select compatible sets of valid trajectories and prove that this scheme guarantees collision-avoidance in the specified setup. The theoretical results have been also experimentally confirmed with a distributed simulator where each vehicle replans online with a samplingbased, kinodynamic motion planner and uses message-passing to communicate with neighboring agents. I.

Abstract: Vehacol or Vehicular Anti-Collision is a mechanism for determining collision course between two or more vehicles. The mechanism uses a combination of physical and logical layer techniques to generate self and remote node information that can be exchanged to enable location awareness. Two vehicles (nodes) periodically exchange information about their individual movement in terms of displacement, speed and direction (with reference to a geographic North). In addition to the information exchange through an ad hoc network, vehicles also measure the separating distance through physical measurement. To do so, the vehicles use a unique but simple modulation format and reception technique that avoids the problems caused by multipath fading. Combining the inputs obtained through the measurement of distance and periodic information exchanges, vehicles are able to determine whether or not they are on a collision course with another vehicle. The paper discusses system parameters, protocol and other design issues related to the implementation of the Vehacol system. Simulation results and assumptions are also presented that validate the mechanism from the perspectives of error computation and discovery times.