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.

Vehicles equipped with wireless communication devices are poised to deliver vital services in the form of safety alerts, traffic congestion probing and on-road commercial applications. Tools to evaluate the performance of vehicular networks are a fundamental necessity. While several traffic simulators have been developed under the Intelligent Transport System initiative, their primary focus has been on modeling and forecasting vehicle traffic flow and congestion from a queuing perspective. In order to analyze the performance and scalability of inter-vehicular communication protocols, it is important to use realistic traffic density, speed, trip, and communication models. Studies on multi-hop mobile wireless routing protocols have shown the performance varies greatly depending on the simulation models employed. We introduce GrooveSim, a simulator for geographic routing in vehicular networks to address the need for a robust, easy-to-use realistic network and traffic simulator. GrooveSim accurately models intervehicular communication within a real street map-based topography. It operates in five modes capable of actual on-road inter-vehicle communication, simulation of traffic networks with thousands of vehicles, visual playback of driving logs, hybrid simulation composed of real and simulated vehicles and easy testscenario generation. Our performance results, supported by field tests, establish geographic broadcast routing as an effective means to deliver time-bounded messages over multiple-hops.

Abstract—Vehicular networks are a very promising technology to increase traffic safety and efficiency and to enable numerous other applications in the domain of vehicular communication. Proposed applications for VANETs have very diverse properties and often require non-standard communication protocols. Moreover, the dynamics of the network due to vehicle movements further complicates the design of an appropriate, comprehensive communication system. In this work, we collect and categorize envisioned applications from various sources and classify the unique network characteristics of vehicular networks. Based on this analysis, we propose five distinct communication patterns that form the basis of almost all VANET applications. Both the analysis and the communication patterns shall deepen the understanding of VANETs and simplify further development of VANET communication systems. Index Terms—Vehicular ad hoc networks (VANETs), applications, communication patterns, network characteristics I.

Realistic simulation is a necessary tool for the proper evaluation of newly developed protocols for Vehicular Ad Hoc Networks (VANETs). Several recent efforts focus on achieving this goal. Yet, to this date, none of the proposed solutions fulfil all the requirements of the VANET environment. This is so mainly because road traffic and communication network simulators evolve in disjoint research communities. We are developing TraNS, an open-source simulation environment, as a step towards bridging this gap. This short paper describes the TraNS architecture and our ongoing development efforts. I.

Abstract. Vehicular ad hoc networks (VANETs) are the technical basis of an envisioned Intelligent transportation system. They offer a wide range of applications improving road safety and driving comfort. Since VANET applications affect safety-of-life, data security in a vehicular system is mandatory. The unique characteristics of VANETs compared to conventional mobile ad hoc networks and sensor networks pose particular challenges for a security solution for vehicular environment. For secure routing a number of approaches exist that have been designed for different environments and security objectives, mostly extending wellknown ad hoc routing protocols. This report systematically reviews the existing solutions and describes them on a comparable level of abstraction. Then, the report compares the solutions with respect to applied security mechanisms and performance criteria. Finally, it analyzes whether the features of the selected approaches meet VANETs requirements. From a high-level perspective the main security objectives (authentication, integrity, potentially non-repudiation) of the reviewed proposals fit well to the potential requirements of secure VANET routing. Since future VANET routing will likely be based on a specific routing protocol that utilizes positions of forwarding, additional security countermeasures are needed. These include mechanisms to ensure location privacy, to protect beaconing and location service as part of the routing protocol, and to prevent specific attacks that exploit the positions carried in data packets. These aspects necessitate the design of a unique security solution for VANETs. Nevertheless, it can also be concluded from analysis of the VANET characteristics that some aspects aid a security solution, such as less power and processing constraints, central registrations and periodic technical inspections, as well as existing law enforcement procedures. 1 ⋆ Also with Universidade de Aveiro, Instituto Telecomunicações, Portugal.

Abstract — Vehicle-to-vehicle (V2V) wireless networks are a special case of mobile ad hoc networks where the topology is constrained to a street map, maximum relative speeds are in excess of 90m/s and the node density spans a large dynamic range reaching over 5,000 vehicles/mi 2. V2V communication aims to make the driving experience safer, more efficient and more enjoyable by delivering vehicle alerts, traffic updates and streaming data across multiple hops. Given the scale and ephemeral connectivity of such networks, it is essential to evaluate V2V network protocols in terms of end-to-end message delay, reachability and persistence with incremental deployment. We propose GrooveNet, a hybrid simulation approach where the same network models are used both in simulation and real mobile test-beds and also allow interaction between real and virtual nodes. GrooveNet accurately models inter-vehicular communication between thousands of vehicles within a real street mapbased topography. It facilitates protocol design, rapid in-vehicle deployment and model validation. GrooveNet supports multiple network interfaces, GPS and events triggered from the vehicle’s on-board computer. Through simulation, we are able to study the message latency, persistence and coverage under various traffic conditions. On-road tests over 400 miles lend insight to required market penetration. I.

Abstract—We discuss the need for bidirectional coupling of network simulation and road traffic microsimulation for evaluating Vehicular Ad Hoc Networks (VANETs) in a simulation framework. As the selection of a mobility model influences the outcome of simulations to a great deal, the use of a representative model is necessary for producing meaningful evaluation results. Based on these observations, we present a hybrid simulation framework composed of the road traffic simulator SUMO and the network simulator OMNeT++. The coupled simulation environment is used for an evaluation of two protocols for incident warning in VANETs.

Simulation of network protocol behavior in Vehicular Ad Hoc Network (VANET) scenarios is strongly demanded for evaluating the applicability of developed network protocols. In this work, we discuss the need for bidirectional coupling of network simulation and road traffic microsimulation for evaluating such protocols. The implemented mobility model, which defines all movement of nodes, influences the outcome of simulations to a great deal. Therefore, the use of a representative mobility model is essential for producing meaningful results. Based on these observations, we developed the hybrid simulation framework Veins (Vehicles in Network Simulation), composed of the network simulator OMNeT++ and the road traffic simulator SUMO. Based on a proof-of-concept study, we demonstrate the advantages and the need for bidirectionally coupled simulation.

Abstract. We consider the problem of optimal next-hop selection in a route between two vehicles, for a simple scenario of Vehicular ad hoc networks (VANETs) on a highway. For a given approximation of the optimal number of hops, we seek the optimal choice of next-hop based on its speed and inter-node distances, so as to maximize the expected route lifetime. Under a Markovian assumption on the process of speed of nodes, we show that the optimal choice of speeds attempts to equalize the lifetimes of adjacent links. A monotone variation property of the speed of relay nodes under the optimal policy is proved. These properties have been confirmed with simulations. The optimal policies and their structures can assist in enhancing the performance of existing VANET routing protocols.

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