Information Dissemination in Urban VANETs

In recent years, Vehicular Ad-hoc NETworks (VANETs) have experienced an intense development phase, driven by academia, industry, and public authorities. On the basis of the obtained results, it is reasonable to expect that VANETs will finally hit the market in the near future. In order to reach commercial success, VANETs must effectively operate during the first years of deployment, when the market penetration rate will be unavoidably low, and, consequently, only a small number of suitably equipped vehicles (VANET-enabled) will be present on the roads. Among the possible strategies to face the initial sparse VANET scenarios, the deployment of an auxiliary network constituted by fixed Road Side Units (RSUs), either Dissemination Points (DPs) or relays, is certainly one of the most promising. In order to maximize the benefits offered by this support infrastructure, the placement of RSUs needs to be carefully studied. In this chapter, the authors analyze, by means of numerical simulations, the performance of an application that leverages on a finite number of DPs for disseminating information to the transiting vehicles. The positions of the DPs are determined through a recently proposed family of optimal placement algorithms, on the basis of proper vehicular mobility traces. The analysis is carried out considering two realistic urban scenarios. In both cases, the performance improvement brought by the use of multi-hop broadcast protocols, with respect to classical single-hop communications with DPs, is investigated.

The Role of Roadside Assistance in Vehicular Communication Networks

Vehicular Communication Networks is a subcategory of Mobile Communications Networks that has the special characteristics of high node mobility and fast topology changes. In the current chapter, the authors outline the basic characteristics and concepts of vehicular communications and present the standardization and network deployment efforts carried out by the scientific community. In particular, they focus their attention on the vehicle-to-infrastructure component of the network; moreover, the authors specifically investigate security, quality of service, and routing, which constitute three of the most challenging aspects in the field of Vehicular Networks. The authors further examine the ways that infrastructure can provide efficient solutions to the problems that exist for each respective category and review several proposed solutions.

WiMAX for Traffic Control in Urban Environments

This chapter addresses the wireless communication aspect of traffic control in an urban vehicular environment. The IEEE 802.16e-2005 standard is used for Infrastructure to Vehicle communication. An architecture is developed with the target of minimizing overall data loss. Access Service Network Gateway (ASN-GW) is used to manage vehicle communication while roaming. OPNET simulations show that using ASN-GW gives good performance in mobility management. Simulations also show that introducing an interference source drastically degrades system performance. Using Dual Trigger HO (DTH) in a congested scenario improves system performance and reduces the impact of interference on the system.

Real Time Acquisition of Traffic Information through V2V, V2R, and V2I Communications

Many vehicles are currently equipped with On-Board Units (OBUs) that are in charge of collecting and processing data for some specific purposes (such as for travel monitoring, as requested by many insurance companies). These devices are connected to the cellular network by means of their Vehicle-to-Infrastructure (V2I) communication interface, and are thus able to transmit and receive information also related to real time traffic, pollution, local events, etc. Of course, as the number of OBU-equipped vehicles increases, the cost of this service increases as well, both in terms of network load and billing. In this chapter, the authors discuss the possibility of taking advantage of vehicle-to-vehicle (V2V) and Vehicle-to-Roadside (V2R) communications to save V2I resources, thus reducing the cellular network burden and, consequently, the service cost.

On-Board Unit Hardware and Software Design for Vehicular Ad-Hoc Networks

Intelligent Transport Systems (ITS) are a focus of public authorities and research communities in order for them to provide effective solutions for improving citizens’ security and lifestyle. The effectiveness of such systems relies on the prompt processing of the acquired traffic- and vehicle-related information to react to congestion and dangerous situations. To obtain a dynamic and pervasive environment where vehicles are fully integrated in the ITS, low cost technologies (capable of strongly penetrating the market) must be made available by the effort of academic and industrial research. In this chapter, the authors discuss the design and implementation of a prototype vehicular unit capable of interacting with both roadside networks and in-vehicle electronic devices. More in detail, in order to scientifically characterize the solution, the authors start from a clear statement of the requirements that the vehicle equipment should respond to. Then they detail the selection of the off-the-shelf components adopted in the prototyped on-board unit. In the last part of the chapter, the authors discuss several possible applications in which the developed device can be adopted, as well as open issues for future research activities.

Infrastructure Assisted Data Dissemination for Vehicular Sensor Networks in Metropolitan Areas

Vehicular Sensor Networks (VSNs) are an emerging area of research that combines technologies developed in the domains of Intelligent Transport Systems (ITS) and Wireless Sensor Networks. Data dissemination is an important aspect of these networks. It enables vehicles to share relevant sensor data about accidents, traffic load, or pollution. Several protocols are proposed for Vehicle to Vehicle (V2V) communication, but they are prone to intermittent connectivity. In this chapter, the authors propose a roadside infrastructure to ensure stable connectivity by adding vehicle to infrastructure to the V2V communication. They introduce a data dissemination protocol, Hexagonal Cell-Based Data Dissemination, adapting it for VSNs within a metropolitan area. The virtual architecture of the proposed data dissemination protocol exploits the typical radial configuration of main roads in a city, and uses them as the basis for the communication infrastructure where data and queries are stored. The design of the communication infrastructure in accordance with the road infrastructure distributes the network data in locations that are close or easily reachable by most of the vehicles. The protocol performs a geographical routing and is suitable for highly dynamic networks, supporting a high number of mobile sources and destinations of data. It ensures reliable data delivery and fast response. The authors evaluate the performance of the proposed protocol in terms of data delivery ratio and data delivery delay. The simulation results show that HexDD significantly improves the data packet delivery ratio in VANETs.

A Novel Distributed QoS Control Scheme for Multi-Homed Vehicular Networks

Resource availability in vehicular mobile networks fluctuates due to wireless channel fading and network mobility. Multi-homed mobile networks require a Quality-of-Service (QoS) control scheme that can select a routing path to guarantee high quality of communications with Correspondent Nodes (CNs) while using the maximum available bandwidth of wireless and radio communication technologies. In this chapter, the authors develop an intelligent distributed QoS control scheme which inter-operates between mobile routers, managing vehicular networks mobility, and Road Communication Gateways (RCGs). This proposed scheme manages Vehicle-to-Infrastructure (V2I) communications through enabling multi-homed vehicular networks to optimally distribute traffic among egress links of their mobile routers based on vehicular communication policies and available bandwidth and performance metrics of selected routing paths. This scheme considers the data control plane as a collaborative entity and specifies detailed operations to be performed in the mobile routers and RCGs. Simulation experiments show that the proposed scheme can improve the Congestion Window (CWND) of TCP and the e2e packet loss of video traffic, despite network mobility. It also guarantees the service parameter settings of uplink and downlink connections while achieving reasonable utilization efficiency of network resources and fairly sharing them.

Employing Traffic Lights as Road Side Units for Road Safety Information Broadcast

There is great concern over growing road accidents and associated fatalities. In order to reduce accidents, improve congestion and offer smooth flow of traffic, several measures, such as providing intelligence to transport, providing communication infrastructure along the road, and vehicular communication, are being undertaken. Traffic safety information broadcast from traffic lights using Visible Light Communication (VLC) is a new cost effective technology which assists drivers in taking necessary safety measures. This chapter presents the VLC broadcast system considering LED-based traffic lights. It discusses the integration of traffic light Roadside Units (RSUs) with upcoming Intelligent Transportation Systems (ITS) architecture. Some of the offered services using this technology in vehicular environment together with future directions and challenges are discussed. A prototype demonstrator of the designed VLC systems is also presented.

RSU Deployment for Content Dissemination and Downloading in Intelligent Transportation Systems

The focus of this chapter is twofold: information dissemination from infrastructure nodes deployed along the roads, the so-called Road-Side Units (RSUs), to passing-by vehicles, and content downloading by vehicular users through nearby RSUs. In particular, in order to ensure good performance for both content dissemination and downloading, the presented study addresses the problem of RSU deployment and reviews previous work that has dealt with such an issue. The RSU deployment problem is then formulated as an optimization problem, where the number of vehicles that come in contact with any RSU is maximized, possibly considering a minimum contact time to be guaranteed. Since such optimization problems turn out to be NP-hard, heuristics are proposed to efficiently approximate the optimal solution. The RSU deployment obtained through such heuristics is then used to investigate the performance of content dissemination and downloading through ns2 simulations. Simulation tests are carried out under various real-world vehicular environments, including a realistic mobility model, and considering that the IEEE 802.11p standard is used at the physical and medium access control layers. The performance obtained in realistic conditions is discussed with respect to the results obtained under the same RSU deployment, but in ideal conditions and protocol message exchange. Based on the obtained results, some useful hints on the network system design are provided.

A Survey on Information Dissemination in VANETs

Vehicular Ad Hoc Network (VANET) has become an active area of research, standardization, and development because next generation vehicles will be capable of sensing, computing, and communicating. Different components in a vehicle constantly exchange available information with other vehicles on the road and cooperate to ensure safety and comfort of users using VANET. In VANET, information like navigation, cooperative collision avoidance, lane changing, speed limit, accident, obstacle, or road condition warnings, location awareness services, etc. play a significant role in safety-related applications. Safety related information dissemination is challenging due to the delay-sensitive nature of safety services. In this chapter, the authors survey some of the ongoing recent research efforts in information dissemination in VANETs. They also outline some of the research challenges that still need to be addressed to enable efficient information dissemination in VANET.