Decentralized Congestion Control Algorithm for Vehicle to Vehicle Networks Using Oscillating Transmission Power

Wireless access in vehicular environments (WAVE) is a vehicle to vehicle (V2V) communications technology which could help prevent up to 82% of non-impaired accidents, according to the US DOT. A 2013 study by the World Health Organization estimated 2,227 road fatalities in 2009 alone. Currently the channel that is responsible for a vehicle’s awareness of others suffers from congestion at moderate loads. In this paper we propose a novel method for adjusting the transmission power in a pattern which alternates between high and low powered transmissions. We modify one commonly used decentralized congestion control (DCC) algorithm, LIMERIC, and compare the power adaptation model against two controls. WAVE supports a 300 meter transmission radius, however, less than 200 vehicles can communicate at the target rate of 10 transmissions per second. We demonstrate that our algorithm reduces the number of packets received by distant vehicles, while maintaining a higher packet rate to the closer vehicles, for which a higher rate is more important

Assessing Mission-critical Vehicular Safety Applications under Various Network Conditions

Enabling communication among vehicles can facilitate the deployment of safety applications that can improve driving safety and reduce traffic-related fatalities. Assessing the reliability of these safety applications is essential to evaluating VANETs' contributions to improved safety and driving conditions. In this context, I maintain that reliability metrics that express the requirements of safety applications in terms of network performance are much more suitable than standalone network-level metrics, as the latter do not indicate whether the requirements of safety applications can be met. This work considers awareness as an intermediate layer between the application and the network layers, for identifying the different levels of reliability achievable by the different safety applications. Through a comprehensive simulation study, this work analyzes the level of awareness that networks can offer under various scenarios and a wide range of influencing parameters, including transmission power, message generation rate, vehicular density, message size, as well as radio propagation and fading effects. Insights are provided on how network performance metrics address application requirements and contribute to enhancing the reliability of safety applications. Finally, communication parameters necessary to offering high levels of reliability are determined for three representative safety-application requirements

Zuverlässigkeitsbewertung von Fahrzeug-zu-Fahrzeug Kommunikation

V2V communication enables a plethora of cooperative applications aimed at reducing road hazard situations as well as enhancing traffic efficiency and individual driving comfort, expanding therewith the boundaries of Advanced Driver Assistance Systems (ADAS). These applications will be supported by IEEE 802.11p, a standard operating in the 5.9GHz frequency band and adapted for the highly dynamic vehicular environment. The focus of this work is V2V safety applications, which have already gained a major attention from the industry, academia, as well as standardization bodies. Being a subject of wireless communication the performance of V2V applications directly depends on the communication link quality and the packet distribution pattern. Therefore, the main purpose of this thesis is to develop an effective communication link reliability assessment method and analyze to what extent V2V communication is feasible to satisfy the reliability requirements of safety applications. Furthermore, we investigate the effectiveness of the proposed assessment method when applied for real-time communication link reliability prediction. In particular, in this work we establish the link between classical network performance metrics and specific application reliability requirements and derive a set of advanced assessment metrics. Afterwards, we investigate through these metrics how different environmental factors affect application reliability based on the measurement data, which was obtained in elaborated real-world measurement campaigns and in different non-line-of-sight scenarios. Using the suggested metrics further in this work we additionally analyze the achievable application reliability of the V2V safety applications in congested network scenarios through the simulation study. Based on these results we also define the most favorable combinations of the network parameters to support reliable operation of these applications. Finally, in this thesis we examine to what extent the suggested metrics are suitable for applications while operating in real time. We develop and implement two frameworks for prediction of the communication link reliability, based on the data that was obtained over the 4.5 months of the simTD project field trials. Furthermore, we apply both frameworks to other measurement data, which was obtained outside the simTD project and assess the effectiveness of both frameworks under independent realistic conditions.Car2Car-Kommunikation ermöglicht eine Vielzahl von kooperativen Anwendungen, welche auf die Unfallverminderung, Verbesserung der Verkehrseffizienz sowie den individuellen Fahrkomfort abzielen und damit die Grenzen von aktiven Fahrerassistenzsystemen erweitern. Im Fokus dieser Dissertation stehen Car2Car-Sicherheitsanwendungen, denen heutzutage bereits große Aufmerksamkeit von Seiten der Industrie, Forschung und diversen Normierungsgremien geschenkt wird. Da alle diese Anwendungen auf drahtloser Kommunikation basieren, ist ihre Leistungsfähigkeit direkt von der Qualität der Kommunikationsverbindung sowie dem Paketverteilungsmuster abhängig. Daher liegt der Hauptfokus dieser Arbeit in der Entwicklung effektiver Methoden zur Bewertung der Kommunikationszuverlässigkeit und der Analyse, inwieweit Car2Car-Kommunikation im Allgemeinen die Anforderungen von Sicherheitsanwendungen erfüllt. Darüber hinaus untersucht diese Doktorarbeit die Effektivität der hier vorgeschlagenen Bewertungsmethoden in Bezug auf die Vorhersage der Kommunikationszuverlässigkeit in Echtzeit-Szenarien. Im Speziellen verbindet diese Arbeit die Welt der klassischen Netzwerkperformance-Metriken mit Car2Car-Anwendungsspezifischen Zuverlässigkeitsanforderungen und stellt als Ergebnis eine Reihe effektiver Bewertungskennzahlen vor. Mithilfe der vorgeschlagenen Metriken wird des Weiteren untersucht, inwieweit verschiedene Umweltfaktoren die Anwendungszuverlässigkeit beeinflussen können. Diese Untersuchung basiert auf Messdaten, die in ausführlichen Feldversuchen in verschiedenen Non-Line-of-Sight-Szenarien gewonnen wurden. Im nächsten Schritt analysiert diese Doktorarbeit die erreichbare Zuverlässigkeit der Car2Car-Sicherheitsanwendungen in Netzwerküberlastungsszenarien anhand einer Simulationsstudie. Als Ergebnis werden die spezifischen Kombinationen der verschiedenen Netzwerkparameter definiert, die einen zuverlässigen Betrieb der Car2Car-Sicherheitsanwendungen gewährleisten können. Zum Abschluss untersucht diese Dissertation, inwieweit die vorgeschlagenen Metriken für die im Echtzeit-Modus funktionierenden Anwendungen geeignet sind. Darüber hinaus werden zwei Frameworks entwickelt und implementiert, welche die Zuverlässigkeit der Kommunikationsverbindung prädizieren. Dies geschieht basierend auf Daten, die während der 4.5 Monate dauernden Feldversuche im Rahmen des simTD Projektes gewonnen wurden. Beide Frameworks werden am Ende anhand unabhängiger Messdaten auf ihre Funktionalität unter realistischen Bedingungen getestet

Performance and Reliability Evaluation for DSRC Vehicular Safety Communication

<p>Inter-Vehicle Communication (IVC) is a vital part of Intelligent Transportation System (ITS), which has been extensively researched in recent years. Dedicated Short Range Communication (DSRC) is being seriously considered by automotive industry and government agencies as a promising wireless technology for enhancing transportation safety and efficiency of road utilization. In the DSRC based vehicular ad hoc networks (VANETs), the transportation safety is one of the most crucial features that needs to be addressed. Safety applications usually demand direct vehicle-to-vehicle ad hoc communication due to a highly dynamic network topology and strict delay requirements. Such direct safety communication will involve a broadcast service because safety information can be beneficial to all vehicles around a sender. Broadcasting safety messages is one of the fundamental services in DSRC. In order to provide satisfactory quality of services (QoS) for various safety applications, safety messages need to be delivered both timely and reliably. To support the stringent delay and reliability requirements of broadcasting safety messages, researchers have been seeking to test proposed DSRC protocols and suggesting improvements. A major hurdle in the development of VANET for safety-critical services is the lack of methods that enable one to determine the effectiveness of VANET design mechanism for predictable QoS and allow one to evaluate the tradeoff between network parameters. Computer simulations are extensively used for this purpose. A few analytic models and experiments have been developed to study the performance and reliability of IEEE 802.11p for safety-related applications. In this thesis, we propose to develop detailed analytic models to capture various safety message dissemination features such as channel contention, backoff behavior, concurrent transmissions, hidden terminal problems, channel fading with path loss, multi-channel operations, multi-hop dissemination in 1-Dimentional or 2-Dimentional traffic scenarios. MAC-level and application-level performance metrics are derived to evaluate the performance and reliability of message broadcasting, which provide insights on network parameter settings. Extensive simulations in either Matlab or NS2 are conducted to validate the accuracy of our proposed models.</p>Dissertatio