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Car-to-X Communication in Heterogeneous Environments [Elektronische Ressource] = Fahrzeug-Umfeld-Kommunikation in heterogenen Szenarien / Christoph Sommer. Betreuer: Falko Dressler

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209 pages
Car-to-X Communication inHeterogeneous Environments—Fahrzeug-Umfeld-Kommunikationin heterogenen SzenarienDer Technischen Fakultät derUniversität Erlangen-Nürnbergzur Erlangung des GradesD O K T O R - I N G E N I E U Rvorgelegt vonChristoph SommerErlangen – 2011Als Dissertation genehmigt vonder Technischen Fakultät derUniversität Erlangen-NürnbergTag der Einreichung: 30. März 2011Tag der Promotion: 06. Juni 2011Dekan: Prof. Dr.-Ing. Reinhard GermanBerichterstatter: Prof. Dr.-Ing. Falko DresslerProf. Ozan K. Tonguz, Ph.D.AbstractThe challenge of designing and evaluating an integral wireless communicationsystem that affords the exchange of data between cars and with infrastructure iscommonly answered only in part. Car-to-X communication systems are generallytreated as operating either only in freeway scenarios or only in urban scenarios,operating either in a completely infrastructure-less or an infrastructure-dependentfashion. It can be argued, however, that in the highly heterogeneous environmentsof real-life deployments such distinctions cannot be made.In the first part of this work, we demonstrate how to take simulative performanceevaluation of Car-to-X communication systems one step beyond current approaches:we present our successful Open Source framework Veins for the co-simulation of com-munication networks and road traffic.
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Car-to-X Communication in
Heterogeneous Environments

Fahrzeug-Umfeld-Kommunikation
in heterogenen Szenarien
Der Technischen Fakultät der
Universität Erlangen-Nürnberg
zur Erlangung des Grades
D O K T O R - I N G E N I E U R
vorgelegt von
Christoph Sommer
Erlangen – 2011Als Dissertation genehmigt von
der Technischen Fakultät der
Universität Erlangen-Nürnberg
Tag der Einreichung: 30. März 2011
Tag der Promotion: 06. Juni 2011
Dekan: Prof. Dr.-Ing. Reinhard German
Berichterstatter: Prof. Dr.-Ing. Falko Dressler
Prof. Ozan K. Tonguz, Ph.D.Abstract
The challenge of designing and evaluating an integral wireless communication
system that affords the exchange of data between cars and with infrastructure is
commonly answered only in part. Car-to-X communication systems are generally
treated as operating either only in freeway scenarios or only in urban scenarios,
operating either in a completely infrastructure-less or an infrastructure-dependent
fashion. It can be argued, however, that in the highly heterogeneous environments
of real-life deployments such distinctions cannot be made.
In the first part of this work, we demonstrate how to take simulative performance
evaluation of Car-to-X communication systems one step beyond current approaches:
we present our successful Open Source framework Veins for the co-simulation of com-
munication networks and road traffic. It allows simulating complex heterogeneous
scenarios with a high degree of realism and allows for road traffic to be influenced
by network communication – a prerequisite for the evaluation of Traffic Information
System (TIS) designs. Veins relies on a coupling of state-of-the-art simulators from
both domains to incorporate validated models for road traffic microsimulation and
network simulation, and extends them for the simulative performance evaluation of
Car-to-X communication systems.
In a second part of this work, we present our Adaptive Traffic Beacon (ATB)
protocol, an evolved beaconing approach to Car-to-X communication for operation
in truly heterogeneous environments. We base its design on lessons learned from
evaluating common approaches to Inter-Vehicle Communication (IVC), identifying
adaptivity as the key property such approaches were lacking. ATB realizes a self-
organizing TIS also able to make use of optionally available Roadside Unit (RSU)
deployments or a Traffic Information Center (TIC). ATB continuously adapts to
sensed network conditions by adjusting the interval between two beacons to utilize
all unused capacity of the wireless channel, but never more. We demonstrate that,
this way, for high-priority access to the medium and co-existant other protocols and
systems, the channel appears virtually unloaded at all times. We conclude this work
with an evaluation of the strengths and weaknesses of ATB when compared with
state-of-the-art hybrid multi-hop flooding and disruption tolerant networking.
1Kurzfassung
Der Herausforderung, ein integrales System zum drahtlosen Austausch von Daten
zwischen Fahrzeugen und mit Infrastruktur zu entwerfen und seine Leistung zu be-
werten, stehen üblicherweise lediglich Teillösungen gegenüber. So legt man Ansätze
zur Fahrzeug-Umfeld-Kommunikation entweder für den Einsatz auf Autobahnen
oder aber in Städten, sowie entweder voll abhängig oder unabhängig von dedizierter
Infrastruktur, aus. Allerdings erscheint eine Unterscheidung dieser Klassen vor dem
Hintergrund teils stark heterogen geprägter Einsatzszenarien oft unmöglich.
Im ersten Teil dieser Arbeit wird deshalb ein Ansatz zur simulativen Leistungsbe-
wertung dieser Systeme vorgestellt, der die Co-Simulation von Netzwerk- und Stra-
ßenverkehr erlaubt. In Form des erfolgreichen Open-Source-Simulationswerkzeugs
Veins unterstützt der vorgestellte Ansatz die realitätsnahe Simulation komplexer
heterogener Szenarien, nicht zuletzt auch durch die Modellierung der Rückwirkung
von Netzwerk- auf Straßenverkehr. Veins greift auf die Kopplung zweier etablierter
Werkzeuge zurück, und integriert damit validierte Modelle zur Simulation von Fahr-
zeugbewegung wie auch von Netzwerkverkehr, die jeweils um Funktionalität zur
Bewertung von Ansätzen zur Fahrzeug-Umfeld-Kommunikation erweitert wurden.
Im zweiten Teil dieser Arbeit wird mit ATB ein neuartiges Protokoll zur Verbrei-
tung von Informationen per periodischem Broadcast vorgestellt, das speziell mit
Augenmerk auf die Heterogenität realistischer Szenarien entworfen wurde. Auf-
bauend auf bei der Evaluation existierender Ansätze gewonnenen Erfahrungen, die
immer wieder deren mangelhafte Adaptivität aufzeigte, gelang es, ein selbstorgani-
sierendes Verkehrsinformationssystem, das optional auch Infrastrukturkomponenten
integrieren kann, zu entwickeln. Ferner ist ATB in der Lage, durch die kontinuierli-
che Anpassung des Broadcast-Intervalls lediglich ungenutzte Kanalkapazität – diese
allerdings vollumfänglich – auszunutzen. Dadurch steht dem Versand hochpriorer
Nachrichten, wie auch zeitgleich betriebenen Protokollen, jederzeit freie Kanalka-
pazität zur Verfügung. Den Abschluß der Arbeit bildet eine umfassende Bewertung
von ATB, insbesondere im direkten Vergleich mit komplementären Ansätzen zur
Fahrzeug-Umfeld-Kommunikation.
3Contents
1 Introduction 7
1.1 Heterogeneity in Car-to-X Communication . . . . . . . . . . . . . . . . 9
1.2 Contribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2 Fundamentals 13
2.1 Network Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.2 Road Traffic . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2.3 Wireless Communication . . . . . . . . . . . . . . . . . . . . . . . . . . 35
2.4 Paradigms and Protocols . . . . . . . . . . . . . . . . . . . . . . . . . . 43
3 Simulating Car-to-X Communications 53
3.1 The Veins Simulation Framework . . . . . . . . . . . . . . . . . . . . . 57
3.2 Performance Metrics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
3.3 Signal Propagation and Shadowing . . . . . . . . . . . . . . . . . . . . 75
3.4 Road Networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
3.5 The Impact of Car-to-X Communication . . . . . . . . . . . . . . . . . 93
3.6 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
4 Engineering Car-to-X Protocols 105
4.1 Deploying MANET in VANETs . . . . . . . . . . . . . . . . . 111
4.2 IVC Systems Based on Cellular Networks . . . . . . . . . . . . . . . . 123
4.3 The Adaptive Traffic Beacon (ATB) Protocol . . . . . . . . . . . . . . . 141
4.4 Design and Characteristics of ATB . . . . . . . . . . . . . . . . . . . . . 145
4.5 Performance Evaluation of ATB . . . . . . . . . . . . . . . . . . . . . . 153
4.6 Comparison of ATB with Flooding/DTN . . . . . . . . . . . . . . . . . 163
4.7 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167
5 Conclusion 169
Bibliography 187
5Chapter 1
Introduction
The use of Car-to-X communication, i.e., the exchange of data between cars and with
infrastructure, for improving driving safety and efficiency has been on the mind of
researchers since at least the often-cited 1939 New York World’s Fair[95]. Here, in
its Futurama exhibit, General Motors revealed utopian visions of what highways and
cities might look like twenty years later. In fact, many of the visions showcased there,
as well as in the exhibit designer’s 1940 book Magic Motorways[16], such as that
“car-to-car radio hook-up might be used to advise a driver nearing an intersection
of the approach of another car or even to maintain control of speed and spacing of
cars in the same traffic lane”, are still being pursued today.
A huge number[81] of research projects have since then been undertaken which
tried to make visions of Intelligent Transportation Systems (ITS) a reality. Among the
most notable of research initiatives were the Japan CACS project (1973–1979), the
European Prometheus project (1986–1995), or the U.S. PATH project (1986–1992).
(a) infrared sender (b) infrared receiver mounted on rear- (c) traffic light phases and speed recom-
at a traffic light view mirror of an equipped vehicle mendation shown in the vehicle
Figure 1.1 – Concept of the 1983 Wolfsburger Welle demonstration project: in-
frastructure-to-car communication based on infrared transceivers is employed
to transmit traffic light phase information to oncoming vehicles; source:[207].
78 1 Introduction
The majority of these initiatives led to working prototypes and successful field
operational tests (Figure 1.1 gives an impression of their level of sophistication);
yet, commercial success failed to match the projects’ promises.
A possible explanation for this can be found in[26]: early approaches were sim-
ply too visionary for their time, commonly focusing on infrastructure-less solutions,
which could not be supported by current technology. The 1980s then saw a shift of
attention from the more long term goals of complete highway automation to nearer-
term goals like driver-advisory functions. However, for the same reasons, attention
shifted also from infrastructure-less to infrastructure-assisted solutions, resulting
in what the authors called a chicken-and-egg type of standoff in the deployment of
IVHS (Intelligent Vehicle-Highway Systems) solutions:
“The automotive and electronics industries are skeptical as to whether
the public infrastructure for IVHS will materialize. (Without an in-
frastructure, of course, there will be no market for cooperative IVHS
products on-board the vehicle or on the highway.)
Highway agencies are skeptical as to whether IVHS technologies will de-
liver solutions to real highway problems. (Without a sound expectation
of public benefit, of course, public investment is unjustified.)”
In the years since this 1990 article, however, these premises have changed
considerably, causing interest in Car-to-X communication research to re-ignite:
first, with the commercial deployment of latest-generation cellular communication
technology, there is now an almost universal infrastructure available.
In fact, commercially available versions of what could be described as early Car-to-X
systems are already on the market, e.g., On Star (1995), BMW Assist (1999),
FleetBoard (2000), and TomTom HD Traffic (2007).
Secondly, computing power has increased many-fold, enabling even complex
and fully-distributed ad hoc systems to process and disseminate data under tight
temporal constraints; the feasibility of such systems had been demonstrated by
successfully deployed projects from the context of Mobile Ad Hoc Network (MANET)
research, leading to the later coining of the term Vehicular Ad Hoc (VANET)
as a promising application of MANETs.
The new-found optimism with regard to Car-to-X communication research can
also be seen expressed in the U.S. FCC’s allocation of the Dedicated Short Range
Communications (DSRC) band in 1999, reserving 75 MHz in the 5.9 GHz region for
the sole use of vehicular short-range wireless communication – a development that
further boosted research.
The renewed interest in Car-to-X communication research was also reflected
in a huge increase in publications and projects are again becoming increasingly
ambitious and more inclusive.

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