Technische Universitat¨ Munchen¨ Lehrstuhl fur¨ Medientechnik A Resource-Efficient IP-based Network Architecture for In-Vehicle Communication Dipl.-Ing. Univ. Mehrnoush Rahmani Vollstandiger¨ Abdruck der von der Fakultat¨ fur¨ Elektrotechnik und Informationstechnik der Technischen Universitat¨ Munchen¨ zur Erlangung des akademischen Grades eines Doktor-Ingenieurs (Dr.-Ing.) genehmigten Dissertation. Vorsitzender: Univ.-Prof. Dr. sc. techn. Andreas Herkersdorf Prufer¨ der Dissertation: 1. Univ.-Prof. Dr.-Ing. Eckehard Steinbach 2. Prof. Dr. rer. nat. Ernst W. Biersack Grande Ecole Telecom Paris/ Frankreich Die Dissertation wurde am 16.03.2009 bei der Technischen UniversitatM¨ unchen¨ eingereicht und durch die Fakultat¨ fur¨ Elektrotechnik und Informationstechnik am 19.06.2009 angenommen. Acknowledgment This dissertation was written during my time as PhD student and research member in the network archi- tecture group at BMW Research and Technology and at the Institute for Media Technology at Technische Universitat¨ Munchen¨ (TUM). I am grateful to both institutes to give me the opportunity for this work. This thesis is the result of three years of work whereby I have been accompanied and supported by many people. It is a pleasure to have the opportunity to express my gratitude to all of them. First, I would like to thank my PhD adviser Prof. Dr.-Ing. Eckehard Steinbach for accepting to supervise me as an external PhD student and for his continuous support. I am grateful to him for his many sugges- tions and for being available whenever I needed his advise. His constructive way of work taught me how to carry on in all difficult situations. I owe him lots of gratitude for challenging me and showing me how to progress. Special thanks goes also to my BMW supervisor, Richard Bogenberger, who kept an eye on the progress of my work and integrated me perfectly in his projects. I thank him for providing me with all facilities I needed for this work. I also would like to express my profound appreciation to Mr. Karl-Ernst Steinberg, head of the department for offering me this position and for his constant support also after the PhD period. I would like to express my special gratitude to Prof. Dr. Ernst Biersack from Eurecom for accepting to be my second PhD adviser. I learnt a lot from him during our cooperative projects over the period of this dissertation. It is a pleasure for me to have him as my second thesis examiner. I also would like to acknowledge the cooperative and friendly atmosphere in BMW Research and Tech- nology which is certainly due to its staff. All of my colleagues supported me during this work. My team colleagues, Wolfgang Hintermaier, Joachim Hillebrand, Dr. Rainer Steffen, Dr. Daniel Herrscher and An- dreas Winckler from the ZT-4 department, Dr. Klaus Gresser, Andreas Laika and Dr. Marc Walessa from the ZT-3 department contributed to the success of this thesis. I am grateful to all of them. I also would like to thank Isaac Trefz, Holger Endt, Champ, Ben Krebs and Martin Pfannenstein for proofreading this thesis. I appreciate the staff of the Institute at TUM for providing a pleasant environment to work during the periods I spent at the university. All students I supervised did an excellent work and contributed a lot to this dissertation. It would not be possible to finish this thesis within three years without their contributions. I thank them all and hope to have the opportunity to support them too in the future. Last but most notably, a great thank goes to my dear parents who always encourage me with the best advises for life. This work would never be done without their infinite support. Also, my younger brother and sister, Alborz and Delaram enrich my life with much love. In the end, I dedicate my most special thank to my future husband, Michael who is my best friend, mentor, ideal and stand in life. Munich, January 2009 Mehrnoush Rahmani Abstract This dissertation investigates various aspects of network design and planning for future in-vehicle data communication. The major issues addressed are network architecture and topology design, network di- mensioning, and resource-efficient streaming by means of traffic shaping and video compression in driver assistance camera systems. Concerning the network architecture and topology design, standardized com- munication protocols from the IT domain are analyzed with respect to the in-vehicle communication requirements. A heterogeneous and all-IP-based network architecture is introduced in two different rep- resentative network topologies as candidate parts of the future overall in-vehicle network. Motivated by the fact that the car is a closed network system where all applications and their transmission scenarios are known a priori, a static network dimensioning method is derived analytically and verified by a self- designed simulation model. Quality of Service and resource usage are analyzed in the proposed network topologies. Traffic shaping is used to reduce the required network resources and consequently the cost. A novel traffic shaping algorithm is presented that outperforms other traffic shapers in terms of resource usage when applied to variable bit rate video sources under certain topology constraints. Video compres- sion algorithms are investigated in driver assistance camera systems to be configured such that negative effects on the system performance are avoided while the overall resource usage is reduced. Finally, an experimental prototype is introduced that demonstrates the applicability of the proposed IP-based network in a real car. Zusammenfassung In der vorliegenden Arbeit werden Konzepte fur¨ die zukunftige¨ Datenkommunikation im Fahrzeug ent- wickelt. Dabei liegen die Schwerpunkte auf dem Entwurf der Netzarchitektur und -topologie, der Netz- dimensionierung, der ressourceneffizienten Ubertragung¨ mittels Verkehrsgestaltung (engl. Traffic-Shap- ing) sowie der Videokompression in Fahrerassistenz-Kamerasystemen. Zunachst¨ werden fur¨ den Ent- wurf der Netzarchitektur und -topologie standardisierte Kommunikationsprotokolle aus dem IT-Bereich bezuglich¨ der Erfullung¨ der Kommunikationsanforderungen im Fahrzeug untersucht. Anschließend wird der Entwurf einer heterogenen und durchgangig¨ auf IP-basierten Netzarchitektur fur¨ zwei Arten von Netz- topologien vorgestellt. Diese sind reprasentativ¨ fur¨ zukunftige¨ mogliche¨ Fahrzeugbordnetze. Ausgehend von einem geschlossenen Kommunikationsnetz im Fahrzeug mit a priori bekannten Applikationen und Ubertragungsszenarien¨ wird eine statische Netzdimensionierungsmethode analytisch hergeleitet und an- hand eines eigens entwickelten Simulationsmodells validiert. Um die benotigten¨ Netzressourcen und somit die Kosten zu reduzieren, wird die Methode des Traffic-Shaping eingesetzt. Hinsichtlich der er- forderlichen Ressourcenbelegung ist der vorgestellte Traffic-Shaping-Algorithmus bei Anwendung in Videoquellen mit variabler Datenrate unter bestimmten Topologiebedingungen allen bekannten Traffic- Shapern uberlegen.¨ Weiterhin werden Videokompressionsalgorithmen fur¨ den Einsatz in Fahrerassistenz- Kamerasystemen untersucht und so konfiguriert, dass negative Einflusse¨ auf die Systemperformanz ver- mieden werden und gleichzeitig die Ressourcenbelegung reduziert wird. Abschließend wird ein proto- typischer Aufbau vorgestellt und die Anwendbarkeit des neu entwickelten IP-basierten Netzes in einem realen Fahrzeug verifiziert. Contents 1 Introduction 1 1.1 Motivation...................................... 1 1.2 Contributions and Outline of this Dissertation . ........... 4 2 State of the Art 7 2.1 An Overview of the Existing Automotive Network Systems . ........... 7 2.1.1 CAN: Controller Area Network . 7 2.1.2 LIN: Local Interconnect Network . ... 9 2.1.3 MOST: Media Oriented Systems Transport . 10 2.1.4 FlexRay................................... 11 2.2 IP/Ethernet-based Networks with QoS Support . ......... 11 2.2.1 Avionic Full-Duplex Switched Ethernet (AFDX) . ....... 15 2.2.2 Audio Video Bridging . 16 2.3 Video Compression and Image Processing in the Car . ....... 18 2.3.1 Video Compression - Basics and Codecs . 18 2.3.2 Image Processing in Driver Assistance Systems . ........ 26 2.4 In-VehicleTraffic ................................ 29 2.4.1 RequirementAnalysis ........................... 30 2.4.2 TrafficModeling .............................. 32 2.5 Summary ...................................... 38 3 Proposed Network Architecture 40 3.1 Heterogeneous IP-based In-Vehicle Network . .......... 40 3.1.1 Considered Network Topologies . 41 3.1.2 Analysis of the Component Effort . 43 3.2 WiredCoreNetwork ................................ 47 3.2.1 AnalyticalModel.............................. 47 3.2.2 SimulationModel ............................. 54 3.3 WirelessPeripheralNetwork . ..... 54 3.3.1 AnalyticalModel.............................. 57 3.3.2 SimulationModel ............................. 58 3.4 Summary ...................................... 59 4 Traffic Shaping for Resource-Efficient In-Vehicle Communication 60 4.1 Traffic Shaping Algorithms . 60 4.2 Analytical and Simulation Analysis . ....... 63 4.2.1 Traffic Shaping in Video Sources . 64 4.2.2 Reshaping.................................. 70 4.2.3 Results ................................... 73 4.3 Prototypical Implementation . ...... 83 vii 4.4 Summary ...................................... 88 5 Video Compression and Image Processing for Driver Assistance Systems 91 5.1 Analysis of Applicable Video Codecs for Driver Assistance Camera Systems . 91 5.1.1 SystemDescription. 92 5.1.2 AppliedMetrics