Performance of CAM based Safety Applications using ITS-G5A MAC in High Dense Scenarios

ETSI ITS-G5 is the current vehicle-to-vehicle communication technology in Europe, which will be standardized by ETSI TC ITS. It is based on IEEE 802.11p and therefore uses a CSMA/CA scheme for Media Access Control (MAC). In this paper we analyze the performance of CAM based safety applications using the ETSI ITS-G5 MAC technology in a challenging scenario with respect to MAC issues: A suitable freeway segment with 6 lanes in each direction. The freeway scenario is thoroughly modeled and implemented in the well known ns-3 simulation environment. Based on this model, the paper shows the performance of CAM based safety applications under MAC challenging conditions. Therefore we provide a set of simulation results resting upon a particular performance metric which incorporates the key requirements of safety applications. Finally we analyze two concrete example scenarios to make a point how reliable CAM based safety applications are in high dense traffic scenarios

Cooperative Relative Positioning for Vehicular Environments

Fahrerassistenzsysteme sind ein wesentlicher Baustein zur Steigerung der Sicherheit im Straßenverkehr. Vor allem sicherheitsrelevante Applikationen benötigen eine genaue Information über den Ort und der Geschwindigkeit der Fahrzeuge in der unmittelbaren Umgebung, um mögliche Gefahrensituationen vorherzusehen, den Fahrer zu warnen oder eigenständig einzugreifen. Repräsentative Beispiele für Assistenzsysteme, die auf eine genaue, kontinuierliche und zuverlässige Relativpositionierung anderer Verkehrsteilnehmer angewiesen sind, sind Notbremsassitenten, Spurwechselassitenten und Abstandsregeltempomate. Moderne Lösungsansätze benutzen Umfeldsensorik wie zum Beispiel Radar, Laser Scanner oder Kameras, um die Position benachbarter Fahrzeuge zu schätzen. Dieser Sensorsysteme gemeinsame Nachteile sind deren limitierte Erfassungsreichweite und die Notwendigkeit einer direkten und nicht blockierten Sichtlinie zum Nachbarfahrzeug. Kooperative Lösungen basierend auf einer Fahrzeug-zu-Fahrzeug Kommunikation können die eigene Wahrnehmungsreichweite erhöhen, in dem Positionsinformationen zwischen den Verkehrsteilnehmern ausgetauscht werden. In dieser Dissertation soll die Möglichkeit der kooperativen Relativpositionierung von Straßenfahrzeugen mittels Fahrzeug-zu-Fahrzeug Kommunikation auf ihre Genauigkeit, Kontinuität und Robustheit untersucht werden. Anstatt die in jedem Fahrzeug unabhängig ermittelte Position zu übertragen, werden in einem neuartigem Ansatz GNSS-Rohdaten, wie Pseudoranges und Doppler-Messungen, ausgetauscht. Dies hat den Vorteil, dass sich korrelierte Fehler in beiden Fahrzeugen potentiell herauskürzen. Dies wird in dieser Dissertation mathematisch untersucht, simulativ modelliert und experimentell verifiziert. Um die Zuverlässigkeit und Kontinuität auch in "gestörten" Umgebungen zu erhöhen, werden in einem Bayesischen Filter die GNSS-Rohdaten mit Inertialsensormessungen aus zwei Fahrzeugen fusioniert. Die Validierung des Sensorfusionsansatzes wurde im Rahmen dieser Dissertation in einem Verkehrs- sowie in einem GNSS-Simulator durchgeführt. Zur experimentellen Untersuchung wurden zwei Testfahrzeuge mit den verschiedenen Sensoren ausgestattet und Messungen in diversen Umgebungen gefahren. In dieser Arbeit wird gezeigt, dass auf Autobahnen, die Relativposition eines anderen Fahrzeugs mit einer Genauigkeit von unter einem Meter kontinuierlich geschätzt werden kann. Eine hohe Zuverlässigkeit in der longitudinalen und lateralen Richtung können erzielt werden und das System erweist 90% der Zeit eine Unsicherheit unter 2.5m. In ländlichen Umgebungen wächst die Unsicherheit in der relativen Position. Mit Hilfe der on-board Sensoren können Fehler bei der Fahrt durch Wälder und Dörfer korrekt gestützt werden. In städtischen Umgebungen werden die Limitierungen des Systems deutlich. Durch die erschwerte Schätzung der Fahrtrichtung des Ego-Fahrzeugs ist vor Allem die longitudinale Komponente der Relativen Position in städtischen Umgebungen stark verfälscht.Advanced driver assistance systems play an important role in increasing the safety on today's roads. The knowledge about the other vehicles' positions is a fundamental prerequisite for numerous safety critical applications, making it possible to foresee critical situations, warn the driver or autonomously intervene. Forward collision avoidance systems, lane change assistants or adaptive cruise control are examples of safety relevant applications that require an accurate, continuous and reliable relative position of surrounding vehicles. Currently, the positions of surrounding vehicles is estimated by measuring the distance with e.g. radar, laser scanners or camera systems. However, all these techniques have limitations in their perception range, as all of them can only detect objects in their line-of-sight. The limited perception range of today's vehicles can be extended in future by using cooperative approaches based on Vehicle-to-Vehicle (V2V) communication. In this thesis, the capabilities of cooperative relative positioning for vehicles will be assessed in terms of its accuracy, continuity and reliability. A novel approach where Global Navigation Satellite System (GNSS) raw data is exchanged between the vehicles is presented. Vehicles use GNSS pseudorange and Doppler measurements from surrounding vehicles to estimate the relative positioning vector in a cooperative way. In this thesis, this approach is shown to outperform the absolute position subtraction as it is able to effectively cancel out common errors to both GNSS receivers. This is modeled theoretically and demonstrated empirically using simulated signals from a GNSS constellation simulator. In order to cope with GNSS outages and to have a sufficiently good relative position estimate even in strong multipath environments, a sensor fusion approach is proposed. In addition to the GNSS raw data, inertial measurements from speedometers, accelerometers and turn rate sensors from each vehicle are exchanged over V2V communication links. A Bayesian approach is applied to consider the uncertainties inherently to each of the information sources. In a dynamic Bayesian network, the temporal relationship of the relative position estimate is predicted by using relative vehicle movement models. Also real world measurements in highway, rural and urban scenarios are performed in the scope of this work to demonstrate the performance of the cooperative relative positioning approach based on sensor fusion. The results show that the relative position of another vehicle towards the ego vehicle can be estimated with sub-meter accuracy in highway scenarios. Here, good reliability and 90% availability with an uncertainty of less than 2.5m is achieved. In rural environments, drives through forests and towns are correctly bridged with the support of on-board sensors. In an urban environment, the difficult estimation of the ego vehicle heading has a mayor impact in the relative position estimate, yielding large errors in its longitudinal component

Towards Vision Zero - V2X Communication for Active Vulnerable Road User Protection

Almost half of the casualties on European roads can be accounted to the group of the so-called Vulnerable Road Users (VRUs). The introduction of V2X Communication makes it possible to extend the awareness horizon of automated and autonomous vehicles, in order to avoid accidents with VRUs. In this paper we learn how V2X communication will protect VRUs, what requirements have to be met, what the key performance metrics are and how different communication and localization technologies perform. The Vision Zero goal is to reduce the road traffic casualties including VRUs to zero

Zero-Baseline Measurements for Relative Positioning in Vehicular Environments

Forward collision warning systems, lane change assistants or cooperative adaptive cruise control are examples of safety relevant applications that rely on accurate relative positioning between vehicles. Current solutions estimate the position of surrounding vehicles by measuring the distance with a RADAR sensor or a camera system. One promising approach to extend the perception range of these sensors is the exchange of GNSS raw data measured from a vehicle to a set of satellites by using a inter-vehicle communication link. The aim of this approach is to cancel correlated errors in both receivers and thus achieving a better relative position estimate. The present paper shows the potential of this differential approach by showing the results of a series of zero-baseline experiments conducted in a simulated environment. The impact of uncorrelated errors that are not canceled out by differentiation, such as noise and multipath, is analyzed in depth and verified by simulations. The results show that in clear sky conditions and in absence of multipath propagation, the baseline of a vehicle can be estimated using GNSS pseudorange double differences with less than one meter of error. Multipath might severely degrade this performance, even in the case of a zero-baseline experiment

Slipstream Cooperative Adaptive Cruise Control - A Conceptual ITS Application for Electric Vehicles

The Electric Vehicle is seen to be one of the most important enablers for a more environmentally friendly mobility of people. Unfortunately, state of the art electric vehicles suffer from a series of problems, with facing a very limited traveling distance compared to gasoline vehicles being one of the most relevant ones. In this paper we present an approach how to reduce the energy consumption while traveling over longer distances by using the slipstream effect behind a vehicle ahead. We show how this can be implemented as a specialized form of cooperative adaptive cruise control, one of the innovative Intelligent Transportation System applications. The paper elaborates in detail on the reliability of the application from the perspective of the current ITS communication technology, by means of two example scenarios, and outlines also on other aspects of implementing Slipstream Cooperative Adaptive Cruise Control for electric vehicles

Analytical Performance Considerations of IEEE 802.11p

This technical report sums up some analytical performance considerations of IEEE 802.11p, based on simplified assumptions. We primarily address Media Access Control (MAC) layer issues as they are particularly challenged by a high number of fast mobile nodes. The main target of this preliminary analysis is to set the scope for a comprehensive simulative performance analysis

Reliable vehicle-autarkic collision detection for railbound transportation

ABSTRACT: In this paper we present the concept for reliable vehicle-autarkic collision detection developed for a Rail Collision Avoidance System (RCAS) that is based on direct train-to-train communication. Similar to existing systems in air and maritime transport, the RCAS approach allows vehicle-autarkic detection of imminent collisions. Designed as a safety overlay system, it shall warn and advise train drivers in such situations. Broadcasted messages shall allow each railway vehicle to assess the traffic situation in its vicinity under all operational conditions. Apart from an onboard localization unit, which relies on satellite navigation signals, the system architecture does not require any other infrastructure

Survey on Ranging Sensors and Cooperative Techniques for Relative Positioning of Vehicles

Future driver assistance systems will rely on accurate, reliable and continuous knowledge on the position of other road participants, including pedestrians, bicycles and other vehicles. The usual approach to tackle this requirement is to use on-board ranging sensors inside the vehicle. Radar, laser scanners or vision-based systems are able to detect objects in their line-of-sight. In contrast to these non-cooperative ranging sensors, cooperative approaches follow a strategy in which other road participants actively support the estimation of the relative position. The limitations of on-board ranging sensors regarding their detection range and angle of view and the facility of blockage can be approached by using a cooperative approach based on vehicle-to-vehicle communication. The fusion of both, cooperative and non-cooperative strategies, seems to offer the largest benefits regarding accuracy, availability and robustness. This survey offers the reader a comprehensive review on different techniques for vehicle relative positioning. The reader will learn the important performance indicators when it comes to relative positioning of vehicles, the different technologies that are both commercially available and currently under research, their expected performance and their intrinsic limitations. Moreover, the latest research in the area of vision-based systems for vehicle detection, as well as the latest work on GNSS-based vehicle localization and vehicular communication for relative positioning of vehicles, are reviewed. The survey also includes the research work on the fusion of cooperative and non-cooperative approaches to increase the reliability and the availability

Where is your Guardian Angel? - Locating and Protecting Vulnerable Road Users

This Keynote presentation reviews current localization and communication technologies for protecting vulnerable road users in urban traffic. Additionally it gives an overview on beyond-state-of-the-art research in this field

Measurement and Analysis of ITS-G5 in Railway Environments

In this paper we present first measurement results of a novel approach in Train-to-Train (T2T) communications. For this measurement campaign an Intelligent Transport System (ITS-G5) communication link was used to investigate the in uences of a railway Environment on a Car-to-Car (C2C) communication standard based system. The measurements cover a wide range of scenarios from urban to rural environments, forest to open field as well as tunnels and crossings under bridges. The investigated measurement categories are channel characteristics, system performance and environmental aspects. The results should clarify, if a technology transfer from road to railway track communications would be expedient