Real Vehicular Ad Hoc Networks Research Articles

APDM: An adaptive multi-priority distributed multichannel MAC protocol for vehicular ad hoc networks in unsaturated conditions

Vehicular ad hoc networks (VANETs) employ multichannel to provide a variety of safety and non-safety applications. Safety applications require reliable and timely transmission, while non-safety applications need high network throughput. IEEE 802.11p and IEEE 1609.4 protocol divide the bandwidth into seven channels. One control channel (CCH) is to serve safety applications and the other six service channels (SCHs) to serve non-safety applications. The IEEE 1609.4 protocol specifies an alternating scheme to allow vehicles to switch between two types of applications. However, the IEEE 1609.4 multichannel media access control (MAC) protocol has limitations on its capability of supporting either delay- or throughput-sensitive applications. In this paper, we propose an adaptive multi-priority distributed multichannel (APDM) MAC protocol for VANETs. Considering that in realistic VANETs, the queue of MAC layer is far from saturated. We assume that generated packets with different priorities arrive at the MAC layer in a Poisson manner. A Markov analytical model is conducted to optimize the packet transmission probabilities and adjust the ratio between CCH interval and SCH interval dynamically according to the real-time traffic in a distributed way. An M/M/1 queue model is then adopted to analyze the time performance. Extensive simulation results show that the APDM MAC protocol can ensure prioritized transmission of safety packets, reduce the transmission delay of packets and enhance the unsaturated and saturated throughput of SCHs.

Modelling of Security Principles Within Car-to-Car Communications in Modern Cooperative Intelligent Transportation Systems

Intelligent transportation systems (ITS) bring advanced applications that provide innovative services for various transportation modes in the area of traffic control, and enable better awareness for different users. Communication connections between intelligent vehicles with the use of wireless communication standards, so called Vehicular Ad Hoc Networks (VANETs), require ensuring verification of validity of provided services as well as services related to transmission confidentiality and integrity. The goal of this paper is to analyze secure mechanisms utilised in VANET communication within Cooperative Intelligent Transportation Systems (C-ITS) with a focus on safety critical applications. The practical part of the contribution is dedicated to modelling of security properties of VANET networks via OPNET Modeler tool extended by the implementation of the OpenSSL library for authentication protocol realisation based on digital signature schemes. The designed models simulate a transmission of authorised alert messages in Car-to-Car communication for several traffic scenarios with recommended Elliptic Curve Integrated Encryption Scheme (ECIES). The obtained results of the throughput and delay in the simulated network are compared for secured and no-secured communications in dependence on the selected digital signature schemes and the number of mobile nodes. The OpenSSL library has also been utilised for the comparison of time demandingness of digital signature schemes based on RSA (Rivest Shamir Adleman), DSA (Digital Signature Algorithm) and ECDSA (Elliptic Curve Digital Signature Algorithm) for different key-lengths suitable for real time VANET communications for safety-critical applications of C-ITS.

Coherent, automatic address resolution for vehicular ad hoc networks

The interest in vehicular communications has increased notably. In this paper, the use of the address resolution (AR) procedures is studied for vehicular ad hoc networks (VANETs).We analyse the poor performance of AR transactions in such networks and we present a new proposal called coherent, automatic address resolution (CAAR). Our approach inhibits the use of AR transactions and instead increases the usefulness of routing signalling to automatically match the IP and MAC addresses. Through extensive simulations in realistic VANET scenarios using the Estinet simulator, we compare our proposal CAAR to classical AR and to another of our proposals that enhances AR for mobile wireless networks, called AR+. In addition, we present a performance evaluation of the behaviour of CAAR, AR and AR+ with unicast traffic of a reporting service for VANETs. Results show that CAAR outperforms the other two solutions in terms of packet losses and furthermore, it does not introduce additional overhead.

Toward Practical and Intelligent Routing in Vehicular Ad Hoc Networks

Apart from vehicle mobility, data rate (bit rate) and multihop data transmission efficiency (including route length) have a significant impact on the performance of a routing protocol for vehicular ad hoc networks (VANETs). Existing routing protocols do not seriously address all these issues and are not evaluated for a real VANET environment. Therefore, it is difficult for these protocols to attain a high performance and to work properly under various scenarios. In this paper, we first discuss the challenges of routing in VANETs based on the data acquired from real-world experiments and then propose a routing protocol that is able to learn the best transmission parameters by interacting with the environment. The protocol takes into account multiple metrics, specifically data transmission rate, vehicle movement, and route length. We use both real-world experiments and computer simulations to evaluate the proposed protocol.

How Close are We to Realizing a Pragmatic VANET Solution? A Meta-Survey

Vehicular Ad-hoc Networks (VANETs) are seen as the key enabling technology of Intelligent Transportation Systems (ITS). In addition to safety, VANETs also provide a cost-effective platform for numerous comfort and entertainment applications. A pragmatic solution of VANETs requires synergistic efforts in multidisciplinary areas of communication standards, routings, security and trust. Furthermore, a realistic VANET simulator is required for performance evaluation. There have been many research efforts in these areas, and consequently, a number of surveys have been published on various aspects. In this article, we first explain the key characteristics of VANETs, then provide a meta-survey of research works. We take a tutorial approach to introducing VANETs and gradually discuss intricate details. Extensive listings of existing surveys and research projects have been provided to assess development efforts. The article is useful for researchers to look at the big picture and channel their efforts in an effective way.

Pemodelan dan Simulasi VANETs Menggunakan Federated Mobility Model; Sebuah Artikel Tinjauan

The emergence of Vehicular Ad-hoc Networks (VANETs) as part of the Intelligent Transportation Systems (ITS) technology development was expected to become an advanced method to solve the transportation system problem. The implementation of VANETs is expected to provide a new solution for traffic management strategy. Its main targets is to continue prioritizing traffic safety and to prevent the accidents on the roads. One of the VANETs problems before being implemented in the real world is the degree of freedom of the vehicle's mobility that limited by the road topologies. Various modellings and simulations have been performed to produce the most realistic mobility model. However, those models had become new paradigms due to various factors that limited them. The presence of the federated mobility model as an approach for traffic mobility modeling is considered to be able to provide more realistic and accurate VANETs simulation. Therefore, this article presents some brief reviews and contrast a number of the simulation and mobility models that have been used widely as compared to the federated mobility models that have developed until the present. The article's objective is to facilitate a better understanding of the traffic mobility modeling for the VANETs simulation that started from the interaction process until the integration between simulators. The understanding of the traffic mobility models will complement the knowledge that enable to perform the simulation of the VANETs implementation approaching the real conditions.

Vehicle Mobility and Communication Channel Models for Realistic and Efficient Highway VANET Simulation

Developing real-time safety and nonsafety applications for vehicular ad hoc networks (VANETs) requires understanding of the dynamics of the network topology characteristics since these dynamics determine both the performance of routing protocols and the feasibility of an application over VANETs. Using various key metrics of interest, including node degree, neighbor distribution, number of clusters, and link duration, we provide a realistic analysis of the VANET topology characteristics over time and space for a highway scenario. In this analysis, we integrate real-world road topology and real-time data extracted from the freeway Performance Measurement System (PeMS) database into a microscopic mobility model to generate realistic traffic flows along the highway. Moreover, we use a more realistic, recently proposed, obstacle-based channel model and compare the performance of this sophisticated model to the most commonly used and more simplistic channel models, including unit disk and lognormal shadowing models. Our investigation on the key metrics reveals that both lognormal and unit disk models fail to provide realistic VANET topology characteristics. We therefore propose a matching mechanism to tune the parameters of the lognormal model according to the vehicle density and a correlation model to take into account the evolution of the link characteristics over time. The proposed method has been demonstrated to provide a good match with the computationally expensive and difficult-to-implement obstacle-based model. The parameters of the proposed model have been validated to depend only on the vehicle traffic density based on the real data of four different highways in California.

Dynamical Topology Analysis Of Vanet Based On Complex Networks Theory

Abstract A Vehicular Ad hoc NETwork (VANET) is a special subset of multi-hop Mobile Ad hoc Networks, in which the vehicles wireless interfaces can communicate with each other, as well as with fixed equipments alongside city roads or highways. Vehicular mobility dynamic characteristics, including high speed, predictable, restricted mobility pattern significantly affect the performance of routing protocols in a real VANET. Based on the existing studies, here we propose a testing network according to the preferential attachment on the degree of nodes and analyze VANET model characteristics for finding out the dynamic topology from the instantaneous degree distribution, instantaneous clustering coefficient and average path length. Analysis and simulation results demonstrate that VANET has a small world network features and is characterized by a truncated scale-free degree distribution with power-law degree distribution. The dynamic topology analysis indicates a possible mechanism of VANET, which might be helpful in the traffic congestion, safety and management.

Network-layer abstraction and simulation of vehicle communication stack

Vehicular ad-hoc networks (VANETs) display many characteristics that are different from the traditional wireless networks, e.g. the rapidly changing topology and short-lived link. The vehicle communication stack is thus redesigned differently from the traditional TCP/IP architecture in order to accommodate these diversities. The network layer bears the function of the reliable routing and delivery of packets from sources to destinations over a highly dynamic path. We investigate the network layer within the vehicle communication stack and present an abstraction approach, with aims at filling the gap between the simplified and the very detailed models by incorporating more realistic routing protocols and network topologies. We study how the network dynamics, as monitored by multiple network performance indicators (e.g. transmission delay, path length, throughput, and loss rate), is affected by various combinations of routing algorithms, packet sizes, moving speeds, communication ranges, processing rates, boundary conditions, and movement patterns. The proposed suite can be modified and expanded easily to incorporate more features of the real VANET, e.g. traffic light control.

Multi-Agent Based Modeling Simulation about VANET

The self-organization characteristics and the interaction between a large numbers of self-organizing vehicles are complexity, to obtain a more accurate model of vehicular Ad-hoc network (VANET) and obtain a more profound comprehension of the complex behavior working mechanism of the vehicle in the VANET environment multi-agent based and bottom-up modeling approach is proposed here. It aims to describe the dynamics of VANET caused by the different behaviors of vehicular. The simulation tool for vehicular misbehaviors is developed with multi-agent. It aims to and be able to effectively reproduce the real VANET scene. Though the multi-agent based modeling the emergent behavior and sudden existing behaviors of VANET entities are well reflected.

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.

A Semi-Deterministic Channel Model for VANETs Simulations

Today's advanced simulators facilitate thorough studies on Vehicular Ad hoc NETworks (VANETs). However the choice of the physical layer model in such simulators is a crucial issue that impacts the results. A solution to this challenge might be found with a hybrid model. In this paper, we propose a semi-deterministic channel propagation model for VANETs called UM-CRT. It is based on CRT (Communication Ray Tracer) and SCME—UM (Spatial Channel Model Extended—Urban Micro) which are, respectively, a deterministic channel simulator and a statistical channel model. It uses a process which adjusts the statistical model using relevant parameters obtained from the deterministic simulator. To evaluate realistic VANET transmissions, we have integrated our hybrid model in fully compliant 802.11 p and 802.11 n physical layers. This framework is then used with the NS-2 network simulator. Our simulation results show that UM-CRT is adapted for VANETs simulations in urban areas as it gives a good approximation of realistic channel propagation mechanisms while improving significantly simulation time.

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.

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.