Moritz Killat

The impact of traffic-light-to-vehicle communication on fuel consumption and emissions

“Smart” vehicles of the future are envisioned to aid their drivers in reducing fuel consumption and emissions by wirelessly receiving phase-shifting information of the traffic lights in their vicinity and computing an optimized speed in order to avoid braking and acceleration maneuvers. Previous studies have demonstrated the potential environmental benefit in small-scale simulation scenarios. To assess the overall benefit, large-scale simulations are required. In order to ensure computational feasibility, the applied simulation models need to be simplified as far as possible without sacrificing credibility. Therefore this work presents the results of a sensitivity analysis and identifies gear choice and the distance from the traffic light at which vehicles are informed as key influencing factors. Our results indicate that a suboptimal gear choice can void the benefits of the speed adaptation. Furthermore, we present first results of a scale-up simulation using a real-world inner-city road network and discuss the range in which we expect the saving in fuel consumption to be in reality.

An empirical model for probability of packet reception in vehicular ad hoc networks

Todays advanced simulators facilitate thorough studies on VANETs but are hampered by the computational effort required to consider all of the important influencing factors. In particular, large-scale simulations involving thousands of communicating vehicles cannot be served in reasonable simulation times with typical network simulation frameworks. A solution to this challenge might be found in hybrid simulations that encapsulate parts of a discrete-event simulation in an analytical model while maintaining the simulations credibility. In this paper, we introduce a hybrid simulation model that analytically represents the probability of packet reception in an IEEE 802.11p network based on four inputs: the distance between sender and receiver, transmission power, transmission rate, and vehicular traffic density. We also describe the process of building our model which utilizes a large set of simulation traces and is based on general linear least squares approximation techniques. The model is then validated via the comparison of simulation results with the model output. In addition, we present a transmission power control problem in order to show the models suitability for solving parameter optimization problems, which are of fundamental importance to VANETs.

Simulative Analysis of Vehicle-to-X Communication considering Traffic Safety and Efficiency

Over the past several years, there has been significant interest and progress in using wireless communication technologies for vehicular environments in order to increase traffic safety and efficiency. Due to the fact that these systems are still under development and large-scale tests based on real hardware are difficult to manage, simulations are a widely-used and cost-efficient method to explore such scenarios. Furthermore, simulations provide a possibility to look at specific aspects individually and to identify major influencing effects out of a wide range of configurations. In this context, we use the HP XC4000 for an extensive and detailed sensitivity analysis in order to evaluate the robustness and performance of communication protocols as well as to capture the complex characteristics of such systems in terms of an empirical model.

Enabling traffic safety assessment of VANETs by means of accident simulations

Vehicular ad hoc networks are conceived as a means to increase traffic safety. Primary means to demonstrate their beneficial impact before deployment are computer simulations that comprise communication models, mobility models of vehicles and models of VANET applications. In particular, the movement behavior of vehicles poses questions when evaluating traffic safety since driver models typically do not allow accidents to happen. In this paper we address modifications to the popular Wiedemann model and present an integration of the modified driving behavior to the traffic simulator VISSIM which thus enables simulations containing accidents. Finally, we show in a simulative study how locally available information on the current traffic situation can contribute to safer road traffic. Our contributions represent a first step on how to assess VANETs with respect to traffic safety.

Vehicle-to-Vehicle Communications: Reception and Interference of Safety-Critical Messages (Fahrzeug-zu-Fahrzeug-Kommunikation: Empfang und Interferenz sicherheitskritischer Nachrichten)

Summary A robust exchange of messages between vehicles via radio communication represents a key problem of vehicular ad hoc network (VANET) research. Environmental influences and the multitude of communicating nodes result in challenging communication conditions that have to be taken into account when assessing the potential benefit of VANETs for traffic safety and efficiency applications. In this paper we discuss an appropriate modeling of three influencing factors on the communication behavior to establish a basis for credible simulation results. In detail, we analyze the effects of fast-fading, capturing, and cumulative noise on vehicular communications and illustrate their considerable influence on a simulations outcome. As a second contribution, we provide an empirical model for the probability of packet reception that is based on the proposed simulation methodology. The model thus allows to determine credible simulation results without being dependent on the complexity of detailed simulations. The saved computational effort facilitates the assessment of VANETs in large-scale scenarios and the consideration of communication specifics in the design process. Zusammenfassung Der robuste Austausch von Nachrichten zwischen Fahrzeugen mittels Funkkommunikation stellt ein wesentliches Problem der Forschung über Fahrzeug-Ad-Hoc-Netzwerke (VANET) dar. Umwelteinflüsse und die große Anzahl miteinander kommunizierender Fahrzeuge verursachen schwierige Kommunikationsbedingungen, die es bei der Abschätzung des möglichen Nutzens von VANETs auf die Verkehrssicherheit und -effizienz zu berücksichtigen gilt. Die vorliegende Arbeit diskutiert eine geeignete Modellierung von Einflussfaktoren auf das Kommunikationsverhalten und schafft damit eine Basis für glaubwürdige Simulationsergebnisse. Wir untersuchen den Einfluss von “Fast Fading” und die Bedeutung von “Packet-Capturing” und diskutieren die Auswirkung von kumuliertem Rauschen auf dem Kommunikationskanal. Für alle Effekte demonstrieren wir ihren entscheidenden Einfluss auf die Ergebnisse einer Simulation. Aufbauend auf dieser detaillierten Modellierung stellen wir ein empirisches Modell vor, das die Empfangswahrscheinlichkeit von Paketen in Abhängigkeit von der Entfernung und der Verkehrsdichte bestimmt. Dieses Modell ermöglicht das Erzielen akkurater Simulationsergebnisse bei reduzierter Komplexität des Simulationsvorgangs. Der eingesparte Rechenaufwand vereinfacht die Simulation von sehr großen Fahrzeugnetzen und die Berücksichtigung von Kommunikationsspezifika in der Anwendungsentwicklung.

A Comprehensive Simulation Tool Set for Cooperative Systems

PRE-DRIVE C2X is a project funded within the 7th Framework Programme of the EU to support the development and introduction of cooperative systems. One major part of this work is the creation of a comprehensive tool set of simulation models integrating all fields of expertise involved. The objective is to create, test and apply an integrated simulation tool set that allows to simulate and evaluate the interaction between vehicle traffic, vehicular communication and co-operative applications. Each of these three areas is treated by dedicated models. Additionally the environmental effects are modelled by a separate modelling approach with detailed algorithms for vehicle dynamics and engine behaviour. The process to arrive at such a model combination from user requirements over pre-existing know-how and other significant steps are described as well as the current status of the work.