Multi-metric Geographic Routing for Vehicular Ad hoc Networks

Maintaining durable connectivity during data forwarding in Vehicular Ad hoc Networks has witnessed significant attention in the past few decades with the aim of supporting most modern applications of Intelligent Transportation Systems (ITS). Various techniques for next hop vehicle selection have been suggested in the literature. Most of these techniques are based on selection of next hop vehicles from fixed forwarding region with two or three metrics including speed, distance and direction, and avoid many other parameters of urban environments. In this context, this paper proposes a Multi-metric Geographic Routing (M-GEDIR) technique for next hop selection. It selects next hop vehicles from dynamic forwarding regions, and considers major parameters of urban environments including, received signal strength, future position of vehicles, and critical area vehicles at the border of transmission range, apart from speed, distance and direction. The performance of M-GEDIR is evaluated carrying out simulations on realistic vehicular traffic environments. In the comparative performance evaluation, analysis of results highlight the benefit of the proposed geographic routing as compared to the state-of-the-art routing protocols

Towards reliable geographic broadcasting in vehicular networks

In Vehicular ad hoc Networks (VANETs), safety-related messages are broadcasted amongst cars, helping to improve drivers' awareness of the road situation. VANETs’ reliability are highly affected by channel contention. This thesis first addresses the issue of channel use efficiency in geographical broadcasts (geocasts). Constant connectivity changes inside a VANET make the existing routing algorithms unsuitable. This thesis presents a geocast algorithm that uses a metric to estimate the ratio of useful to useless packet received. Simulations showed that this algorithm is more channel-efficient than the farthest-first strategy. It also exposes a parameter, allowing it to adapt to channel load. Second, this thesis presents a method of estimating channel load for providing feedback to moderate the offered load. A theoretical model showing the relationship between channel load and the idle time between transmissions is presented and used to estimate channel contention. Unsaturated stations on the network were shown to have small but observable effects on this relationship. In simulations, channel estimators based on this model show higher accuracy and faster convergence time than by observing packet collisions. These estimators are also less affected by unsaturated stations than by observing packet collisions. Third, this thesis couples the channel estimator to the geocast algorithm, producing a closed-loop load-reactive system that allows geocasts to adapt to instantaneous channel conditions. Simulations showed that this system is not only shown to be more efficient in channel use and be able to adapt to channel contention, but is also able to self-correct suboptimal retransmission decisions. Finally, this thesis demonstrates that all tested network simulators exhibit unexpected behaviours when simulating broadcasts. This thesis describes in depth the error in ns-3, leading to a set of workarounds that allows results from most versions of ns-3 to be interpreted correctly

AN ADAPTIVE INFORMATION DISSEMINATION MODEL FOR VANET COMMUNICATION

Vehicular ad hoc networks (VANETs) have been envisioned to be useful in road safety and many commercial applications. The growing trend to provide communication among the vehicles on the road has provided the opportunities for developing a variety of applications for VANET. The unique characteristics of VANET bring about new research challenges

Data Communication in VANETs: Survey, Applications and Challenges

International audienceVANETs have emerged as an exciting research and application area. Increasingly vehicles are being equipped with embedded sensors, processing and wireless communication capabilities. This has opened a myriad of possibilities for powerful and potential life-changing applications on safety, efficiency, comfort, public collaboration and participation, while they are on the road. Although, considered as a special case of a Mobile Ad Hoc Network, the high but constrained mobility of vehicles bring new challenges to data communication and application design in VANETs. This is due to their highly dynamic and intermittent connected topology and different application's QoS requirements. In this work, we survey VANETs focusing on their communicationand application challenges. In particular, we discuss the protocol stack of this type of network, and provide a qualitative comparison between most common protocols in the literature. We then present a detailed discussion of dfferent categories of VANET applications. Finally, we discuss open research problems to encourage the design of new VANET solutions

A RELIABILITY-BASED ROUTING PROTOCOL FOR VEHICULAR AD-HOC NETWORKS

Vehicular Ad hoc NETworks (VANETs), an emerging technology, would allow vehicles to form a self-organized network without the aid of a permanent infrastructure. As a prerequisite to communication in VANETs, an efficient route between communicating nodes in the network must be established, and the routing protocol must adapt to the rapidly changing topology of vehicles in motion. This is one of the goals of VANET routing protocols. In this thesis, we present an efficient routing protocol for VANETs, called the Reliable Inter-VEhicular Routing (RIVER) protocol. RIVER utilizes an undirected graph that represents the surrounding street layout where the vertices of the graph are points at which streets curve or intersect, and the graph edges represent the street segments between those vertices. Unlike existing protocols, RIVER performs real-time, active traffic monitoring and uses this data and other data gathered through passive mechanisms to assign a reliability rating to each street edge. The protocol then uses these reliability ratings to select the most reliable route. Control messages are used to identify a node’s neighbors, determine the reliability of street edges, and to share street edge reliability information with other nodes

Analysis and application of hop count in multi-hop wireless ad-hoc networks

Hop count, i.e., the number of wireless hops a packet has to go through to reach the destination, is a fundamental metric in multi-hop wireless ad-hoc networks. Network performance, such as throughput, end-to-end delay, energy consumption, and so on, depends critically on hop count. Previous work on modeling hop count is limited in making unrealistic simplifying assumptions either at the physical or network, or both layers of the communication protocol stack. A key contribution of this thesis is to present an analytical model to derive the probability distribution of hop count under realistic assumptions at both physical and network layers. Specifically, the model considers a log-normal shadowing radio propagation capable of accommodating the random signal fading observed in most wireless communication environments, and the widely used geographic routing at the network layer. Validation of the model is achieved by a comprehensive set of simulation experiments including a trace driven simulation of a real-word vehicular ad-hoc network. The model reveals that the presence of randomness in radio propagation reduces the required number of hops to reach a given destination significantly. To demonstrate the utility of the proposed hop count model, the thesis proposes three new applications which address some of the key challenges in multi-hop wireless networks. The first application derives the per-node packet forwarding load in multi-hop wireless sensor networks and reveals that the nodes in the vicinity of the base station has a significantly less forwarding load than previously thought under simplifying radio propagation and routing assumptions. The second application demonstrates that using hop count as a measure of distance traveled by a data packet, geocasting can be achieved in multi-hop wireless networks in situations when some of the network nodes do not have access to reliable location information. Finally, the proposed hop count model is used to evaluate the performance of the third application which demonstrates that the overhead of geographic routing can be reduced significantly by embracing a position update philosophy which adapts to the mobility and communication patterns of the underlying ad-hoc network

Analyzing the Impact of Wireless Multi-Hop Networking On Vehicular Safety

One of the core challenges of Intelligent Transportation System is the dissemination of timely and accurate vehicle information (e.g. speed, position) to geographically large distances without compromising data supply rates from immediate neighbors. This feature is critical for the design of vehicle safety and navigation applications. Single hop broadcasting is often inadequate to ensure vehicle safety when the platoon size is arbitrarily large due to its upper bound on rate and range of wireless message transmission. Existing wireless multi-hop protocols do not ensure reliable message delivery while avoiding network congestion in the shared channel. In this thesis, we make two separate but related investigations to address this challenge - (1) Analyze the impact of distance sensitive multi-hop broadcasting in realistic traffic network (2) Analyze the impact of wireless multi-hop network in vehicle safety. For investigating the first part, we used VCAST, a distance sensitive information propagation technique, in which information is forwarded at a rate that decreases linearly with distance from the source. VCAST is evaluated by using extensive simulations in ns-3, a discrete event simulator for wireless and mobile ad-hoc networks, under different density, source broadcast rates and communication range. To simulate realistic traffic movement, we used 2d grids of different sizes and used both uniform and non-uniform mobility. The results show that VCAST is scalable for - large number of vehicles and large source broadcast rates. It is further shown that successful scaling is achieved by reduced number of vehicle records transmitted per second per vehicle for varying network sizes and varying source broadcast rates. Vehicle safety messages for VCAST are piggy backed on heart beat messages and does not require any modifications to the existing vehicular communication standards. For investigating the second part, we implemented a realistic car following model and used string stability analysis as a metric for measuring vehicle safety. The basic idea is to exploit the small network propagation time in disseminating safety messages over large distances, instead of relying on just the predecessor vehicle\u27s state. This enables distant vehicles in a traffic stream to plan well in advance against rear end collisions which could lead to string instability. We also proposed one such proactive method of planning - and that is by controlling the headway time. Through extensive simulations, we obtained results for vehicle safety when some incident is detected abruptly on its course. The results show that proactive planning using multi-hop network makes the entire platoon string stable in the presence of emergency road incidents

Advanced Transport Protocols for Wireless and Mobile Ad Hoc Networks

This thesis comprises transport protocols in the following different areas of research: Fast Handover allows mobile IP end-devices to roam between wireless access routers without interruptions while communicating to devices in an infrastructure (e.g., in the Internet). This work optimizes the Fast Handover algorithm and evaluates the performance of the transport protocols UDP and TCP during fast handovers via measurements. The following part of the thesis focuses on vehicular ad hoc networks. The thesis designs and evaluates through simulations a point-to-point transport protocol for vehicular ad hoc networks and an algorithm to facilitate the reliable and efficient distribution of information in a geographically scoped target area. Finally, the thesis evaluates the impact of wireless radio fluctuations on the performance of an Ad Hoc Network. Measurements quantify the wireless radio fluctuations. Based on these results, the thesis develops a simple but realistic radio model that evaluates by means of simulations the impact on the performance of an ad hoc network. As a result, the work provides guidelines for future ad hoc protocol design

Broadcasting Protocol for Effective Data Dissemination in Vehicular Ad Hoc Networks

VANET topology is very dynamic due to frequent movements of the nodes. Using beacon information connected dominated set are formed and nodes further enhanced with neighbor elimination scheme. With acknowledgement the inter section issues are solve. A modified Broadcast Conquest and Delay De-synchronization mechanism address the broadcasting storm issues. Although data dissemination is possible in all direction, the performance of data dissemination in the opposite direction is investigated and compared against the existing protocols

A Presence-Based Architecture for a Gateway to Integrate Vehicular Ad-Hoc Networks (VANETs), the IP Multimedia Subsystems (IMS) and Wireless Sensor Networks (WSNs)

Résumé Le IP Multimedia Subsystems (IMS) est un sujet de recherche qui attire l’attention de la communauté de recherche. Il a comme but de fournir un accès mobile aux différents services internet. Il s’agit d’une architecture de contrôle au-dessus de la couche IP dont le but est de fournir une qualité de service, services intégrés et un système de tarification équitable à travers des interfaces standards. D’autre part, le réseau Ad-hoc de véhicules (VANETs) fournit un nouveau moyen de communication sans-fil entre les véhicules circulants à grande vitesse ainsi que les équipements installés tout au long des côtés de la route. Cette technologie ouvre la porte pour développer des applications diverses comme la génie de trafic, gestion du trafic, diffusion d’information en cas d’urgence pour éviter des situations critiques, divertissement et bien d’autres choses. VANETs forme une sous-classe des réseaux Ad-hoc mobile dont la performance est fortement liée au protocole de routage utilisé dans le réseau. L’intégration des deux technologies, IMS et VANET, permettra de mettre en œuvre de nouveaux services multimédias. Ce mémoire de maîtrise propose une architecture d’une passerelle incorporant ces deux technologies ensemble. Étant donné que les deux architectures utilisent des formats de communication différents, on a conçu un middleware afin d’adapter le format en fonction de la destination et de choisir la meilleur stratégie de livraison d’information entre eux. La passerelle, qui est le cœur de notre architecture, est une couche au-dessus du IMS et le VANET. ----------ABSTRACT On one hand, IP Multimedia Subsystems (IMS) are a research area that has been gaining attention from the research community. It aims to provide cellular access to all Internet services. It is a control architecture on the top of the IP layer whose goal is dependent on the provision of the Quality of Service (QoS), integrated services and fair charging scheme throughout standard interfaces. On the other hand, Vehicular Ad-hoc Networks (VANETs) are a new communication paradigm that enables the wireless communication between vehicles moving with high speeds, as well as the vehicles and the road side equipments found along the roads. This opened the door to develop several new applications like, traffic engineering, traffic management, dissemination of emergency information to avoid critical situations, comfort and entertainment and other user applications. Moreover, VANETs are a sub-class of mobile ad-hoc networks; the performance of the communication depends on how better the routing takes place in the network. Routing of data depends on the routing protocols being used in the network. Combining the capabilities of IMS world with the VANET world opens the door to deploy a wide range of novel multimedia services. This dissertation proposes a presence-based architecture for the integration of IMS with VANETs. The presence of the middleware is used to make an instantaneous awareness of the VANETs changes as well as of the IMS format and to select the best delivery strategy between the two architectures. The gateway which is the heart of our architecture is an overlay built on the top of the IMS as well as the VANETs