IEEE 802.11 is an economical and efficient standard that has been applied to vehicular networks. However, the long handoff latency of the standard handoff scheme for IEEE 802.11 has become an important issue for seamless roaming in vehicular environments, as more handoffs may be triggered due to the higher mobility of vehicles. This thesis presents a new and fast location-based handoff scheme particularly designed for vehicular environments. With the position and movement direction of a vehicle and the locations of the surrounding APs, our protocol is able to accurately predict several possible APs that the vehicle may visit in the future and to assign these APs different priority levels. APs on higher priority levels will be first scanned. Once a response to scanning from an AP is received, the scanning process ends immediately. A blacklist scheme is also used to exclude those APs that showed no response to the scanning during previous handoffs. Thus, time spent on scanning APs is supposed to be significantly reduced. The simulation results show that the proposed scheme attains not only a lower prediction error rate, but also a lower MAC layer handoff latency, and that it has a smaller influence on jitter and throughput; moreover, these results show that the proposed scheme has a smaller total number of handoffs than other handoff schemes.

Vehicular ad hoc Networks (VANETs) allow vehicles to form a self-organized network. VANETs are likely to be widely deployed in the future, given the interest shown by industry in self-driving cars and satisfying their customers various interests. Problems related to Mobile ad hoc Networks (MANETs) such as routing, security, etc.have been extensively studied. Even though VANETs are special type of MANETs, solutions proposed for MANETs cannot be directly applied to VANETs because all problems related to MANETs have been studied for small networks. Moreover, in MANETs, nodes can move randomly. On the other hand, movement of nodes in VANETs are constrained to roads and the number of nodes in VANETs is large and covers typically large area. The following are the contributions of the thesis. Secure, authenticated, privacy preserving message dissemination in VANETs: When vehicles in VANET observe phenomena such as accidents, icy road condition, etc., they need to disseminate this information to vehicles in appropriate areas so the drivers of those vehicles can take appropriate action. When such messages are disseminated, the authenticity of the vehicles disseminating such messages should be verified while at the same time the anonymity of the vehicles should be preserved. Moreover, to punish the vehicles spreading malicious messages, authorities should be able to trace such messages to their senders when necessary. For this, we present an efficient protocol for the dissemination of authenticated messages. Incentive-based architecture for vehicular cloud: Due to the advantages such as exibility and availability, interest in cloud computing has gained lot of attention in recent years. Allowing vehicles in VANETs to store the collected information in the cloud would facilitate other vehicles to retrieve this information when they need. In this thesis, we present a secure incentive-based architecture for vehicular cloud. Our architecture allows vehicles to collect and store information in the cloud; it also provides a mechanism for rewarding vehicles that contributing to the cloud. Privacy preserving message dissemination in VANETs: Sometimes, it is sufficient to ensure the anonymity of the vehicles disseminating messages in VANETs. We present a privacy preserving message dissemination protocol for VANETs.

<p>Accident statistics indicate that every year a significant number of casualties and extensive property losses occur due to traffic accidents. Consequently, efforts are directed towards developing passive and active safety systems that help reduce the severity of crashes, or prevent vehicles from colliding with one another. To develop these systems, technologies such as sensor systems, computer vision and vehicular communication have been proposed. Safety vehicular communication is defined as the exchange of data between vehicles with the goal of providing in-vehicle safety systems with enough information to permit detection of traffic dangers. Inter-vehicle communication is a key safety technology, especially as a complement to other technologies such as radar, as the information it provides cannot be gathered in any other way. However, due to the specifics of the traffic environment, the design of efficient safety communication systems poses a series of major technical challenges.</p><p>In this thesis we focus on the design and development of a safety communication system that provides support for active safety systems such as collision warning and collision avoidance. We begin by providing a method for designing the support system for active safety systems. Within our study, we investigate different safety aspects of traffic situations. For performing traffic investigations, we have developed ECAM, a temporal reasoning system for modeling and analyzing accident scenarios.</p><p>Next, we focus on the communication system design. We investigate approaches that can be applied to implement safety vehicular communication, as well as design aspects of such systems, including networking techniques and transmission procedures. We then propose a new solution for vehicular communication in the form of a distributed communication protocol that allows the vehicles to organize themselves in virtual clusters according to their common interest in traffic safety. To disseminate the information used for organizing the network and for assessing dangers in traffic, we develop an anonymous context-based broadcast protocol. This protocol requires the receivers to determine whether they are the intended destination for sent messages based on knowledge about their current situation in traffic. This communication system is then augmented with a reactive operation mode, where warnings can be issued and forwarded by vehicles. A vehicular communication platform that provides an implementation framework for the communication system, and integrates it within a vehicle, is also proposed. Experiments have been conducted, under various conditions, to test communication performance and the system’s ability to reduce accidents. The results indicate that that the proposed communication system can efficiently provide the exchange of safety information between vehicles.</p>

<p>Wireless communication is of great importance for safety and entertainment purposes in vehicular networks. Vehicles on roads are required to share sensor data, road traffic information or digital maps with other vehicles on the road. To be able to do this, vehicles require to either communicate directly with each other or to be connected to a wireless communication-based access points on the road side. These wireless access points support short to medium range wireless communication through the protocol 802.11p. 802.11p is designed specifically for vehicular communication and it is an amended form of the widely used 802.11 protocol suit for wireless local area networks (WLAN). Vehicles are able to be associated with these wireless access points for exchange of information. While vehicles move along the road infrastructure, they change their point of attachment from one wireless access point to another wireless access point. During this process, connectivity to the access point breaks down until the vehicle is connected to a new access point in its area. This disconnection causes an interruption in the data flow. This interruption increases when vehicle requires a new IP address, i.e. when the vehicle is going to attach to an access point which is part of another network. In this thesis report, we give an overview of standard handover methods and their enhancements and propose a fast handover scheme for layer 3 of the communication stack. Based on the assumption that vehicles know their route in advance, we enhance the handover process and improve seamless connectivity. We also discuss different issues which are the cause of delay and how they can be overcome in our proposed solution.</p>

Accident statistics indicate that every year a significant number of casualties and extensive property losses occur due to traffic accidents. Consequently, efforts are directed towards developing passive and active safety systems that help reduce the severity of crashes, or prevent vehicles from colliding with one another. To develop these systems, technologies such as sensor systems, computer vision and vehicular communication have been proposed. Safety vehicular communication is defined as the exchange of data between vehicles with the goal of providing in-vehicle safety systems with enough information to permit detection of traffic dangers. Inter-vehicle communication is a key safety technology, especially as a complement to other technologies such as radar, as the information it provides cannot be gathered in any other way. However, due to the specifics of the traffic environment, the design of efficient safety communication systems poses a series of major technical challenges. In this thesis we focus on the design and development of a safety communication system that provides support for active safety systems such as collision warning and collision avoidance. We begin by providing a method for designing the support system for active safety systems. Within our study, we investigate different safety aspects of traffic situations. For performing traffic investigations, we have developed ECAM, a temporal reasoning system for modeling and analyzing accident scenarios. Next, we focus on the communication system design. We investigate approaches that can be applied to implement safety vehicular communication, as well as design aspects of such systems, including networking techniques and transmission procedures. We then propose a new solution for vehicular communication in the form of a distributed communication protocol that allows the vehicles to organize themselves in virtual clusters according to their common interest in traffic safety. To disseminate the information used for organizing the network and for assessing dangers in traffic, we develop an anonymous context-based broadcast protocol. This protocol requires the receivers to determine whether they are the intended destination for sent messages based on knowledge about their current situation in traffic. This communication system is then augmented with a reactive operation mode, where warnings can be issued and forwarded by vehicles. A vehicular communication platform that provides an implementation framework for the communication system, and integrates it within a vehicle, is also proposed. Experiments have been conducted, under various conditions, to test communication performance and the system’s ability to reduce accidents. The results indicate that that the proposed communication system can efficiently provide the exchange of safety information between vehicles.

Video dissemination capabilities are crucial for the deployment of many services over VANETs. These services range from enhancing safety via the dissemination of video from the scene of an accident, to advertisement of local services or businesses. This work considers the infrastructure-less scenario of VANETs and dissemination of video content over this network environment, which is extremely challenging mainly due to its dynamic topology and stringent requirements for video streaming. This study discusses issues and challenges that need to be tackled for disseminating high-quality video over VANETs. Furthermore it surveys and analyzes the suitability of different existing solutions aimed towards effective and efficient techniques for video dissemination in vehicular networks. As a result, a set of the most promising techniques are selected, described in detail and evaluated based on standard terms in quality of service. This thesis also discusses efficiency and suitability of these techniques for video dissemination and compares their performance over the same network condition. In addition, a detailed study on the effect of network coding on video dissemination protocols has been conducted to guide how to employ this technique properly for video streaming over VANETs. From this study, a summary of the observations was obtained and used to design a new hybrid solution by deploying robust and efficient techniques in number of existing protocols in an optimal manner. The proposed hybrid video dissemination protocol outperforms other protocols in term of delivery ratio and complies with other quality-of-service requirements for video broadcasting over vehicular environments.

This thesis examines the problem of using 802.11 hotspots for vehicular Internet access. In this access paradigm, a user in a vehicle performs batch transfers by opportunistically communicating with roadside 802.11 access points while driving along a highway. Despite the short connection duration, a significant amount of data can be transferred. Because complete coverage is not needed, this method of Internet access provides a low-cost alternative to using cellular technology for applications that can tolerate some delay and require large data transfer such as sending or receiving music, movies, or digital photographs. Although vehicular opportunistic connections offer the potential to transfer a large of amount of data, utilizing this potential is non-trivial because existing transport and data-link layer network protocols were not designed for this use. This thesis presents an experimental analysis of transport and data-link layer protocol operation at a level of detail not previously explored. We identify ten problems that cause a reduction of up to 50% of the amount of data that could have been transferred in this scenario. Our primary finding is that transmission errors during connection setup and inadequate MAC data rate selection are the main causes of the under-utilization of the connection. Based on these findings we make preliminary recommendations for best practices for using vehicular opportunistic connections. In particular, we argue that overall throughput could be significantly improved if environmental information was available to the lower layer network protocols.

Wireless communication is of great importance for safety and entertainment purposes in vehicular networks. Vehicles on roads are required to share sensor data, road traffic information or digital maps with other vehicles on the road. To be able to do this, vehicles require to either communicate directly with each other or to be connected to a wireless communication-based access points on the road side. These wireless access points support short to medium range wireless communication through the protocol 802.11p. 802.11p is designed specifically for vehicular communication and it is an amended form of the widely used 802.11 protocol suit for wireless local area networks (WLAN). Vehicles are able to be associated with these wireless access points for exchange of information. While vehicles move along the road infrastructure, they change their point of attachment from one wireless access point to another wireless access point. During this process, connectivity to the access point breaks down until the vehicle is connected to a new access point in its area. This disconnection causes an interruption in the data flow. This interruption increases when vehicle requires a new IP address, i.e. when the vehicle is going to attach to an access point which is part of another network. In this thesis report, we give an overview of standard handover methods and their enhancements and propose a fast handover scheme for layer 3 of the communication stack. Based on the assumption that vehicles know their route in advance, we enhance the handover process and improve seamless connectivity. We also discuss different issues which are the cause of delay and how they can be overcome in our proposed solution.

This thesis examines the problem of using 802.11 hotspots for vehicular Internet access. In this access paradigm, a user in a vehicle performs batch transfers by opportunistically communicating with roadside 802.11 access points while driving along a highway. Despite the short connection duration, a significant amount of data can be transferred. Because complete coverage is not needed, this method of Internet access provides a low-cost alternative to using cellular technology for applications that can tolerate some delay and require large data transfer such as sending or receiving music, movies, or digital photographs. Although vehicular opportunistic connections offer the potential to transfer a large of amount of data, utilizing this potential is non-trivial because existing transport and data-link layer network protocols were not designed for this use. This thesis presents an experimental analysis of transport and data-link layer protocol operation at a level of detail not previously explored. We identify ten problems that cause a reduction of up to 50% of the amount of data that could have been transferred in this scenario. Our primary finding is that transmission errors during connection setup and inadequate MAC data rate selection are the main causes of the under-utilization of the connection. Based on these findings we make preliminary recommendations for best practices for using vehicular opportunistic connections. In particular, we argue that overall throughput could be significantly improved if environmental information was available to the lower layer network protocols.

Wireless research and development requires effective and efficient simulation and emulation tools to validate and evaluate wireless designs. Wireless channel models are used in the tools to simulate signal propagation properties in the real physical world. However, due to practical issues, these models are often too generalized and simplified in large scale experiments, and they only provide limited realism. In this thesis, a novel world model is proposed for simulation and emulation of wireless networks. The proposed model includes the design and implementation of a variety of environment models that enhance realism in simulation. These models capture realistic signal propagation properties across multiple connections, and over time: first, the impact of realistic physical world features, such as channel dynamics and cross link correlation are characterized at different time scales; then, both geometrical and statistical simulation models are developed to recreate desired channel dynamics among wireless network links efficiently. Three major components of the proposed design are described in this thesis: 1) a flexible channel simulation model, 2) improvement of parameter accuracy in geometric channel models, and 3) wireless link correlation models with a case study in vehicular networks. The flexible channel simulation model supports fast generation of channel updates for complicated channel models, including small-scale fast fading, large-scale path loss and multi-path delay and attenuation. To achieve high realism, a variety of techniques are developed to obtain high parameter accuracy in geographic channel models. Link correlation models are developed for simulating wireless channels within a network context, where adjacent wireless links share the same propagation medium. The wireless link correlation model handles both temporal and spatial correlations, to reflect properties at different time scales and location-based similarities. A case study in vehicular networks illustrates the effectiveness of using the proposed environment model to improve the realism of wireless simulation and emulation platforms. Simulation results from implemented models are compared against the measurement data from physical world vehicle-to-vehicle channels, and show good approximation to reality. The evaluation results of correlated channel models show improved realism in channel properties and corresponding impact on the performance of a gossip protocol.