Mobility Models of Vehicular Networks

A key component for VANET simulations is a realistic vehicular mobility model that ensures conclusions drawn from simulation experiments will carry through to real deployments. However, VANET simulations raise many new questions about suitable levels of details in simulation models. To get accurate results, the mobility models of Vehicular Networks should be as realistic as possible, and involve road-maps with all constraints and facilities related to the vehicular movement. In this chapter, the authors provide an overview of some mobility models that are relevant to VANETs. The criteria of applicability they consider here is the employment of road maps, and thus limiting the nodes movements into the routes, instead of moving them in a wide open area. They compare different models based on the parameters they use. For instance, some models use traffic control mechanisms (stop signs or traffic lights) at route intersections, and some just assume continuous movement at these points. Some assume routes to be single-lane, some others support multi-lanes routes. Some define the security distance, while others just ignore this parameter.

MOVE

Vehicular Ad-Hoc Network (VANET) is surging in popularity, in which vehicles constitute the mobile nodes in the network. Due to the prohibitive cost of deploying and implementing such a system in real world, most research in VANET relies on simulations for evaluation. A key component for VANET simulations is a realistic vehicular mobility model that ensures conclusions drawn from simulation experiments will carry through to real deployments. However, VANET simulations raise many new questions about suitable levels of details in simulation models for nodes mobility. In VANET simulations, the mobility models used affect strongly the simulation output. The researchers need to decide what level of details are required for their simulations. In this chapter, the authors introduce a tool MOVE that allows users to rapidly generate realistic mobility models for VANET simulations. MOVE is built on top of an open source micro-traffic simulator SUMO. The output of MOVE is a realistic mobility model and can be immediately used by popular network simulators such as ns-2 and Qualnet. The authors show that the simulation results obtained when using a realistic mobility model such as MOVE are significantly different from results based on the commonly used random waypoint model. In addition, the authors evaluate the effects of details of mobility models in three case studies of VANET simulations (specifically, the existence of traffic lights, driver route choice and car overtaking behavior) and show that selecting sufficient level of details in the simulation is critical for VANET protocol design.

DTN Technologies for Vehicular Networks

A Delay Tolerant Network (DTN) is one type of challenged network where network contacts are intermittent or link performance is highly variable or extreme. In such a network, a complete path does not exist from source to destination for most of the time. In addition, the path can be highly unstable and may change or break unexpectedly. To make communication possible in a delay tolerant network, the intermediate nodes need to take custody of data during the blackout and forward it toward the destination when the connectivity resumes. A vehicular network nicely falls into the context of DTN since the mobility of vehicles constantly causes the disruption of link connectivity’s between vehicles. In this chapter, the authors discuss some research challenges and issues which might occur in a Delay Tolerant Network and how they are related to vehicular networks.

Remote Vehicular System Management Functions and Information Structure

Due to the rapid development of information technology, the network has already spread to every corner of vehicle. With all kinds of ECU devices appear in the vehicle, and it brings the more and more convenient living. On purpose solving heterogamous technologies that are incompatible with each other, developed a “WBEM-based Remote Management and Heterogeneous Vehicular Network Diagnosis System” on OSGi Gateway. This system can focus on a variety of problems come from vehicle network, and find out what are the problems or where are the problems happened. If the problem still can not be solved properly, we must to seek for help from remote managers. The users can acquire enough information without understanding how to control every device, so that the users can help near diagnosis system to solve vehicle network’s problems and to promote the abilities of near network diagnosis.

Vehicular System Management Architecture and Application Platform

Notably, not all telematics services can be used in telematics terminals as a result of the varied platform standards. The main issues are that most telematics technologies depend on vertical, proprietary and closed per-OEM Original Equipment Manufacture (OEM) platforms, forming islands of non-interoperable technology and preventing third-party service providers from creating valuable services. In this study, the Open Gateway Service Initiative Vehicle Expert Group (OSGi/VEG) was integrated into an Android platform to generate a vehicular Android/OSGi platform that has the advantages of both original platforms, such as remote management, rich class sharing, proprietary vehicular applications, security policies, easy management of application programming interface (APIs), and an environment with increased openness. Furthermore, this study integrates the cloud computing mechanism into the Android/OSGi platform, which allows service providers to upload their telematics bundles onto storage clouds via the provisioning server.

Routing Protocols in Vehicular Ad Hoc Networks

Vehicular Ad hoc Network (VANET), a subclass of mobile ad hoc networks (MANETs), is a promising approach for the intelligent transportation system (ITS). The design of routing protocols in VANETs is important and necessary issue for support the smart ITS. The key difference of VANET and MANET is the special mobility pattern and rapidly changeable topology. It is not effectively applied the existing routing protocols of MANETs into VANETs. In this chapter, we mainly survey new routing results in VANET. The authors introduce unicast protocol, multicast protocol, geocast protocol, mobicast protocol, and broadcast protocol. It is observed that carry-and-forward is the new and key consideration for designing all routing protocols in VANETs. With the consideration of multi-hop forwarding and carryand- forward techniques, min-delay and delay-bounded routing protocols for VANETs are discussed in VANETs. Besides, the temporary network fragmentation problem and the broadcast storm problem are further considered for designing routing protocols in VANETs. The temporary network fragmentation problem caused by rapidly changeable topology influence on the performance of data transmissions. The broadcast storm problem seriously affects the successful rate of message delivery in VANETs. The key challenge is to overcome these problems to provide routing protocols with the low communication delay, the low communication overhead, and the low time complexity.

Using Wireless Mesh Network for Traffic Control

Wireless mesh networks (WMN) have attracted considerable interest in recent years as a convenient, flexible and low-cost alternative to wired communication infrastructures in many contexts. However, the great majority of research on metropolitan-scale WMN has been centered around maximization of available bandwidth, suitable for non-real-time applications such as Internet access for the general public. On the other hand, the suitability of WMN for missioncritical infrastructure applications remains by and large unknown, as protocols typically employed in WMN are, for the most part, not designed for realtime communications. In this chapter, we describe a real-world testbed, which sets a goal of designing a wireless mesh network architecture to solve the communication needs of the traffic control system in Sydney, Australia. This system, known as SCATS (Sydney Coordinated Adaptive Traffic System) and used in over 100 cities around the world, connects a hierarchy of several thousand devices -- from individual traffic light controllers to regional computers and the central Traffic Management Centre (TMC) - and places stringent requirements on the reliability and latency of the data exchanges. We discuss some issues in the deployment of this testbed consisting of 7 mesh nodes placed at intersections with traffic lights, and show some results from the testbed measurements.

Applications in Vehicular Ad Hoc Networks

The various sensors and wireless communication devices have been extensively applied to daily life due to the advancements of microelectronics mechanism and wireless technologies. Recently, vehicular communication systems and applications become more and more important to people in daily life. Vehicular communication systems that can transmit and receive information to and from individual vehicles have the potential to significantly increase the safety of vehicular transportation, improve traffic flow on congested roads, and decrease the number of people of deaths and injuries in vehicular collisions effectively. This system relies on direct communication between vehicles to satisfy the communication needs of a large class of applications, such as collision avoidance, passing assistance, platooning. In addition, vehicular communication systems can be supplemented by roadside infrastructure to access Internet and other applications. This system forms a special case of mobile ad hoc networks called Vehicle Ad Hoc Networks (VANETs). They can be formed between vehicles with vehicle to vehicle (V2V) communication or between vehicles and an infrastructure with vehicle to infrastructure (V2I) communication. The applications and characteristics of VANETs are introduced and presented in this Chapter.

MAC Protocols in Vehicular Ad Hoc Networks

With the rapid development of wireless technologies, the Vehicular Ad Hoc Networks (VANETs) have recently received much attention. VANETs technologies aim to ensure traffic safety for drivers, provide comfort for passengers and reduce transportation time and fuel consumption with many potential applications. The achievement of these aims highly relies on efficient MAC protocols which determine the performance of packet transmission in terms of success rate, delay, throughput and bandwidth utilization. This chapter reviews the existing MAC protocols developed for VANETs. Initially, the IEEE 802.11p and DSRC standard are reviewed. Three TDMA-based MAC protocols, called CVIA, VeSOMAC and D*S, are then introduced. In addition, three MAC protocols that cope with the emergency-message broadcasting problem are proposed. Finally, a reliable MAC protocol which is developed based on the cluster topology is reviewed.

Interworking of IP Multimedia Subsystem and Vehicular Communication Gateway

In recent years, more and more people dream of experiencing various IP-based multimedia application services when they are driving through their car. However, those multimedia devices in the car may use different communication protocols such as X.10, Havi, Jini, UPnP and SIP. In order to provide a variety of IP-based multimedia services to those users in the car, the authors mainly investigate the issue of interworking between IP Multimedia Subsystem (IMS) and telematics of the vehicular industry. A service-integrated platform, Open Service Gateway Initiative Service Platform (OSGi SP), has been proposed to act as a Residential Gateway (RGW) and to administer the communication between the vehicular environment and Internet. Besides, a Home IMS Gateway (HIGA), which can be implemented on a NGN RGW, has been developed by Home Gateway Initiative (HGI) since 2005 to collect the relevant information of in-car users, devices and services and to manage the IMS sessions for the in-car devices that do not support IMS functions. With these techniques, the users can enjoy their digital life by interacting with the home/vehicular network from anywhere.