Vehicular Ad Hoc Networks Scenarios Research Articles

Game Approach for Handover Scheme Based on Road-section in VANET

In VANET (Vehicular Ad Hoc Network), vehicles moving from one RSU’s coverage region to another will cause access congestion problem if vehicles use improper handover scheme. In this paper, we present a novel mobility handover scheme for vehicles with seamless Internet access in urban VANET scenario, which is called Game approach for Handover Scheme based on Road-section (GHSR). The main advantages of our scheme are that it uses Sequential Game and it based on 802.11p standard proceeding from service and the vehicles needing to handover will game each other to gain no smaller payoff by selecting an appropriate road-section. Performance evaluations demonstrate that our scheme outperforms the threshold scheme significantly in terms of both the traffic load of RSUs and the QoS (Quality of Service) of vehicles users, and QoS of vehicle users increase by up to 33.68%. 

VeMAC: A TDMA-Based MAC Protocol for Reliable Broadcast in VANETs

The need of a medium access control (MAC) protocol for an efficient broadcast service is of great importance to support the high-priority safety applications in vehicular ad hoc networks (VANETs). This paper introduces VeMAC, a novel multichannel TDMA MAC protocol proposed specifically for a VANET scenario. The VeMAC supports efficient one-hop and multihop broadcast services on the control channel by using implicit acknowledgments and eliminating the hidden terminal problem. The protocol reduces transmission collisions due to node mobility on the control channel by assigning disjoint sets of time slots to vehicles moving in opposite directions and to road side units. Analysis and simulation results in highway and city scenarios are presented to evaluate the performance of VeMAC and compare it with ADHOC MAC, an existing TDMA MAC protocol for VANETs. It is shown that, due to its ability to decrease the rate of transmission collisions, the VeMAC protocol can provide significantly higher throughput on the control channel than ADHOC MAC.

Evaluating the impact of a novel message dissemination scheme for vehicular networks using real maps

In traffic safety applications for vehicular ad hoc networks (VANETs), some warning messages have to be urgently disseminated in order to increase the number of vehicles receiving the traffic warning information. In those cases, redundancy, contention, and packet collisions due to simultaneous forwarding (usually known as the broadcast storm problem) are prone to occur. In the past, several approaches have been proposed to solve the broadcast storm problem in multi-hop wireless networks such as Mobile ad hoc Networks (MANETs). Among them we can find counter-based, distance-based, location-based, cluster-based, and probabilistic schemes, which have been mainly tested in non-realistic simulation environments. In this paper, we present the enhanced Message Dissemination based on Roadmaps (eMDR), a novel scheme specially designed to increase the percentage of informed vehicles and reduce the notification time; at the same time, it mitigates the broadcast storm problem in real urban scenarios. We evaluate the impact that our scheme has on performance when applied to VANET scenarios based on real city maps, and the results show that it outperforms previous schemes in all situations.

Intelligent OLSR Routing Protocol Optimization for VANETs

Recent advances in wireless technologies have given rise to the emergence of vehicular ad hoc networks (VANETs). In such networks, the limited coverage of WiFi and the high mobility of the nodes generate frequent topology changes and network fragmentations. For these reasons, and taking into account that there is no central manager entity, routing packets through the network is a challenging task. Therefore, offering an efficient routing strategy is crucial to the deployment of VANETs. This paper deals with the optimal parameter setting of the optimized link state routing (OLSR), which is a well-known mobile ad hoc network routing protocol, by defining an optimization problem. This way, a series of representative metaheuristic algorithms (particle swarm optimization, differential evolution, genetic algorithm, and simulated annealing) are studied in this paper to find automatically optimal configurations of this routing protocol. In addition, a set of realistic VANET scenarios (based in the city of Malaga) have been defined to accurately evaluate the performance of the network under our automatic OLSR. In the experiments, our tuned OLSR configurations result in better quality of service (QoS) than the standard request for comments (RFC 3626), as well as several human experts, making it amenable for utilization in VANET configurations.

Enhancing VANET Connectivity Through Roadside Units on Highways

In vehicular ad hoc network (VANET) safety applications, the source vehicle that detects an accident can generate a warning message and propagate it to the following vehicles to notify other drivers before they reach the potential danger zone on the road. Recent studies have shown that sparse vehicle traffic leads to network fragmentation, which poses a crucial research challenge for safety applications. In this paper, we analyze and quantify the improvement in VANET connectivity when a limited number of roadside units (RSUs) are deployed and to investigate the routing performance for broadcast-based safety applications in this enhanced VANET environment. Our results show that, even with a small number of RSUs, the performance in terms of the probability of network connectivity, the rehealing delay, the number of rehealing hops, and the message penetration time can be significantly improved in highway VANET scenarios.

An opportunistic forwarding protocol with relay acknowledgment for vehicular ad hoc networks

AbstractRobust and efficient data delivery in vehicular ad hoc networks (VANETs) with high mobility is a challenging issue due to unstable wireless links and dynamic topology changes. In this vehicular environment, the exchanges of topology information and discoveries of routing paths on an end‐to‐end basis are not desired, because the network topology changes rapidly and the information is out‐of‐date in short. In this paper, we propose a contention based forwarding mechanism, which locally exploits geographic location information in order to achieve robustness of data delivery for vehicular communications. A node that is closer to the destination node has a higher priority in competing for the wireless channel, and forwards packets as a relay node earlier than other adjacent nodes. When a packet is forwarded by a relay node, its preceding node informs adjacent nodes that it has been already relayed to prevent the duplications of packet delivery. Through ns‐2 simulations, we show that the proposed scheme can significantly improve the network performance in terms of the packet delivery ratio and the end‐to‐end delay in various synthetic and trace‐based realistic VANET scenarios with a wide range of vehicle speed and density. Copyright © 2010 John Wiley & Sons, Ltd.

A stochastic learning automata‐based solution for intrusion detection in vehicular ad hoc networks

AbstractA number of security concerns are associated with vehicular ad hoc networks (VANET) – some primarily related with the transmission issues between the vehicles and the base stations, while others related with the privacy of the end‐users. Security in VANET is of significant importance, considering the scale of the possible deployment of VANET and their role as a traffic manager. In this paper, we propose an intrusion detection system (IDS) for a typical VANET scenario. Our solution approach is underlain on the concepts of learning automata (LA). To the best of our knowledge, no attempts have been made so far to develop any LA‐based solution for VANETs. We have designed this system considering the privacy issues involved with the identification of each vehicle. We have evaluated the performance of our proposed solution by conducting a variety of experiments and have found our solution approach to be effective in detecting malicious packets in the system. Specifically, the proposed solution is capable of detecting up to around 90–95% of the malicious packets in the system. Copyright © 2010 John Wiley & Sons, Ltd.

Automatic tuning of communication protocols for vehicular ad hoc networks using metaheuristics

The emerging field of vehicular ad hoc networks (VANETs) deals with a set of communicating vehicles which are able to spontaneously interconnect without any pre-existing infrastructure. In such kind of networks, it is crucial to make an optimal configuration of the communication protocols previously to the final network deployment. This way, a human designer can obtain an optimal QoS of the network beforehand. The problem we consider in this work lies in configuring the File Transfer protocol Configuration (FTC) with the aim of optimizing the transmission time, the number of lost packets, and the amount of data transferred in realistic VANET scenarios. We face the FTC with five representative state-of-the-art optimization techniques and compare their performance. These algorithms are: Particle Swarm Optimization (PSO), Differential Evolution (DE), Genetic Algorithm (GA), Evolutionary Strategy (ES), and Simulated Annealing (SA). For our tests, two typical environment instances of VANETs for Urban and Highway scenarios have been defined. The experiments using ns- 2 (a well-known realistic VANET simulator) reveal that PSO outperforms all the compared algorithms for both studied VANET instances.

An interoperability system for authentication and authorisation in VANETs

Vehicular ad hoc networks (VANETs) have evolved considerably over the last years, but despite the wide number of potential applications, VANETs also raise a broad range of critical security and privacy challenges. To achieve privacy, VANETs enforce the concepts of authentication and authorisation via public key infrastructures, relying on a large set of regional certification authorities with explicit cross-certification agreements to provide interoperability for vehicles and services. To avoid the burden of managing these cross-certificates, our research proposes the interoperability system (IS), an architecture to provide VANETs' nodes with a security mechanism for mutually untrusted domains. The IS supplies vehicles with a trusted set of credentials by implementing a certificate status service and a security level evaluator. This paper shows that the proposed architecture can be used to implement a mandatory access control mechanism in two VANET scenarios with a protocol independent of the underlying communication system.

Small-Scale and Large-Scale Routing in Vehicular Ad Hoc Networks

A vehicular ad hoc network (VANET) is a highly mobile wireless ad hoc network that is targeted to support vehicular safety, traffic monitoring, and other applications. Mobility models used in traditional mobile ad hoc networks cannot directly be applied to VANETs since real-world factors such as road layouts and traffic regulations are not considered. In this paper, we propose a vehicular mobility model that reflects real-world vehicle movement and study the performance of packet-routing protocols. First, we study the routing in small-scale VANETs and propose two routing schemes: (1) connection-based restricted forwarding (CBRF) and (2) connectionless geographic forwarding (CLGF). With the insights obtained, we consider routing in large-scale VANETs. Since road complexity and traffic variety may cause many potential problems that existing routing protocols cannot address, we introduce a two-phase routing protocol (TOPO) that incorporates road map information. The proposed protocol defines an <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">overlay</i> graph with roads of high vehicular density and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">access</i> graphs that are connected to the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">overlay</i> . While in the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">overlay</i> , packets are forwarded along a precalculated path. As far as <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">access</i> routing is concerned, we employ the aforementioned CBRF and CLGF schemes and send packets to the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">overlay</i> or handle packets delivered from the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">overlay</i> . We argue that the TOPO can serve as a framework that integrates existing VANET routing protocols. We also consider data diversity in VANETs and design the TOPO as an <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">intelligent transportation system (ITS)-friendly</i> protocol. To validate our design philosophy and the routing protocol, we use different areas in the city of Orlando, FL, and generate vehicular mobility traces, following our mobility models. We feed the traces to network simulators and study the routing behavior. Simulation results demonstrate the performance and effectiveness of the proposed routing protocols for large-scale VANET scenarios.

ACAR: Adaptive Connectivity Aware Routing for Vehicular Ad Hoc Networks in City Scenarios

Multi-hop vehicle-to-vehicle communication is useful for supporting many vehicular applications that provide drivers with safety and convenience. Developing multi-hop communication in vehicular ad hoc networks (VANET) is a challenging problem due to the rapidly changing topology and frequent network disconnections, which cause failure or inefficiency in traditional ad hoc routing protocols. We propose an adaptive connectivity aware routing (ACAR) protocol that addresses these problems by adaptively selecting an optimal route with the best network transmission quality based on statistical and real-time density data that are gathered through an on-the-fly density collection process. The protocol consists of two parts: 1) select an optimal route, consisting of road segments, with the best estimated transmission quality, and 2) in each road segment of the chosen route, select the most efficient multi-hop path that will improve the delivery ratio and throughput. The optimal route is selected using our transmission quality model that takes into account vehicle densities and traffic light periods to estimate the probability of network connectivity and data delivery ratio for transmitting packets. Our simulation results show that the proposed ACAR protocol outperforms existing VANET routing protocols in terms of data delivery ratio, throughput and data packet delay. Since the proposed model is not constrained by network densities, the ACAR protocol is suitable for both daytime and nighttime city VANET scenarios.