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Implementation of Radio Communication and Multi-Hop Data Forwarding

Jul 05, 2015

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ALBERT-LUDWIGS-UNIVERSITY OF FREIBURG DEPARTMENT OF COMPUTER SCIENCE

Implementation of Radio Communication and Multi-hop Data Forwarding in Player/Stage Robot Simulator

Bachelors ThesisTo obtain the grade Bachelor of Science presented by

Michael Sebastian Schrder oat

Computer Networks and Telematics Professor: Prof. Dr. Christian Schindelhauer Advisor: M.Eng. Chia Ching Ooi July 2007

AssertionI hereby avouch that the presented work was written by myself using solely the resources mentioned. All pieces that I paraphrased or quoted literally have been labeled accordingly. This Bachelors thesis was neither used in total nor in extraction for any other work.

Freiburg, July 31, 2007

You see, wire telegraph is a kind of a very, very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? And radio operates exactly the same way: you send signals here, they receive them there. The only dierence is that there is no cat. 1 Albert Einstein

AbstractOver the few past decades the scientic robotic community has been concerned with the dominating competencies of mechanics, control theory and electronics. In recent years, and particularly with the extensive availability of wireless communication devices, more attention has been drawn to communications. Questions about the ecient and coordinated accomplishments of certain tasks by a team of autonomous mobile robots are now one exploratory focus. Likewise, over the years there has been signicant progress in the eld of robot simulators. Modern simulators do not only visualise robots in their particular environment, but provide sophisticated algorithms for localisation, path-planning and mapping, among others. One that is widely used is the Player/Stage robot simulator. The objective of this work is to extend this simulator towards a simulation environment in which mobile robots are enabled to communicate with each other with respect to their current radio connectivity. A model that simulates a wireless network device and focuses on the propagation of radio waves is implemented, as well as a simple data forwarding mechanism, which facilitates client programs.

1

Unsourced citation, attributed to Einstein

ZusammenfassungIn den letzten Jahrzehnten wurde die Wissenschaft der Robotik mageblich durch Mechanik, Kontrolltheorie und Elektronik dominiert. In letzter Zeit und vor allem durch die weitreichende Verfgbarkeit drahtloser Netzwerke, wurde der Kommuu nikation zwischen mobilen Robotern immer mehr Beachtung geschenkt. Fragen nach der ezienten und koordinierten Bewltigung bestimmter Aufgaben, a durch ein Team mobiler autonomer Roboter, bilden heute einen Schwerpunkt der Robotik. Ebenfalls gab es in den letzten Jahren weitreichende Entwicklungen auf dem Gebiet der Robot-Simulatoren. Moderne Simulatoren ermglichen nicht nur die Visualo isierung der Roboter in ihrer jeweiligen Umgebung sondern stellen weitgehende Algorithmen, wie etwa zur Lokalisierung, Pfadplanung oder Kartographierung bereit. Ein sehr bekannter und bewhrter Robotsimulator ist das Player/Stage-System. a Ziel dieser Arbeit ist es diese Simulationsumgebung derart zu erweitern, dass mobile autonome Roboter in der Lage sind, unter Bercksichtigung ihrer gegenwrtigen u a drahtlosen Verbindungsinformationen, zu kommunizieren. Ein Modul wird implementiert, welches unter besonderer Beachtung der Ausbreitung von Radiowellen eine drahtlose Netzwerkschnittstelle simuliert. Weiterhin wird ein Plug-in Treiber fr Player entwickelt, der grundlegende Forwarding-Funktionalitt bietet und das u a Schreiben von Robot-Kontroll-Programmen vereinfacht.

AcknowledgementsI want to thank M.Eng. Chia Ching Ooi for her supervision, guidance and useful suggestions that helped a lot in writing this thesis. Special thanks go to my father who supported me throughout my studies and always encourages me on my future career plans.

List of Figures

1.1 2.1 2.2 2.3 2.4 2.5 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 4.1 4.2 4.3 4.4 4.5

Wireless ad-hoc networking overview . . . . . . . . . . . . . . . . . Example: Player server on ActivMedia robot Example conguration le . . . . . . . . . . . Pioneer 2dx robot in Stage simulation . . . . . Robot conguration in Stage worldle . . . . . Player/Stage simulation overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Overview of radio device . . . . . . . . . . . . . . . . . . . . Implementation overview . . . . . . . . . . . . . . . . . . . . Stage worldle properties for simple radio propagation model Stage worldle properties for free space model . . . . . . . . Worldle properties for ITU indoor model . . . . . . . . . . Worldle properties for Log Distance Path Loss Model . . . Worldle properties for Simple Raytracing model . . . . . . Connectivity visualisation by Simple Raytracing model . . . Structure of communication plug-in driver Conguration for communication driver . . Robot discovers injured person . . . . . . . Robot forwards fallback message . . . . . Message received by all nodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

List of Tables

2.1 2.2 3.1 3.2

Comparison between Stage and Gazebo . . . . . . . . . . . . . . . . 7 Available device models in Stage . . . . . . . . . . . . . . . . . . . 11 Link budget to determine connectivity . . . . . . . . . . . . . . . . 16 Methods by Radio Communication Module . . . . . . . . . . . . . . 18

C.1 Power loss coecients . . . . . . . . . . . . . . . . . . . . . . . . . 45 C.2 Floor penetration loss factor . . . . . . . . . . . . . . . . . . . . . . 45

Contents

1 Introduction 1.1 Wireless Networking Background 1.2 Network Simulators . . . . . . . . 1.3 Robot Simulators . . . . . . . . . 1.4 Motivation . . . . . . . . . . . . . 1.5 Objective . . . . . . . . . . . . . 1.6 Structure of thesis . . . . . . . .

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2 The Player/Stage Robot Simulator 2.1 The Robot Server Player . . . . . . 2.1.1 Devices, Interfaces, Drivers . 2.1.2 Conguration les . . . . . 2.2 Device Simulator Stage . . . . . . . 2.2.1 Device models . . . . . . . . 2.2.2 Stage worldle . . . . . . . 2.2.3 Player and Stage . . . . . .

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3 Radio Communication Module for Stage 3.1 Preliminaries . . . . . . . . . . . . . . . 3.1.1 Radio Propagation . . . . . . . . 3.2 Implementation . . . . . . . . . . . . . . 3.2.1 Radio Communication Module . . 3.2.2 Player Interface . . . . . . . . . . 3.2.3 Radio Communication in Player . 3.3 Implemented Radio Propagation Models

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CONTENTS 3.3.1 3.3.2 3.3.3 3.3.4 3.3.5 Simple Model . . . . . . . . . . Free Space Model . . . . . . . . ITU Indoor Path Loss Model . Log Distance Path Loss Model . Simple Raytrace Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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4 Radio Communication Plug-in Driver 4.1 Implementation . . . . . . . . . . . . 4.2 Conguration . . . . . . . . . . . . . 4.3 Example Scenario . . . . . . . . . . . 4.4 Capabilities . . . . . . . . . . . . . .

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5 Conclusion 34 5.1 Future Works . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 Appendices A Conguration les B Player Client Programs C Coecients for Radio Propagation models 39 39 42 45

1. IntroductionA team of mobile robots approaches carefully, yet in a coordinated manner, the border of a crater and analyses the near environment. In a rescue scenario, multiple robots scour through a hazardous area in search of victims. A group of autonomous UAVs (Unmanned Aerial Vehicle) observes and tracks down a suspicious target in a reconnaissance mission. In all of the above scenarios, the coordination of robots is of vital importance in order to accomplish a certain task eciently. While coordination takes place on a higher and more abstract level, one essential competency of a group of autonomous mobile robots is the ability to communicate. A hardwired infrastructure for mobile robots is conceivably unsuitable. Due to the advancements of radio communication technology in recent years, r