Multi-purpose Embedded Communication Gateway: System Design and Testbed Implementation Chi Winth Ea Morten Sørbø Lei Jiao This master’s thesis is carried out as a part of the education at the University of Agder and is therefore approved as a part of this education. However, this does not imply that the University answers for the methods that are used or the conclusions that are drawn. University of Agder, 2014 Faculty of Information and Communication Technology Department of Engineering and Science Chi Winth Ea Multi-purpose Embedded Communication Gateway: Morten Sørbø System Design and Testbed Implementation Version Control Version Status Date Change Author 0.1 Draft 2014-05-11 Chapters 1, 2 and 3 CWE 0.2 Draft 2014-05-18 All chapters changed CWE and MS 0.3 Draft 2014-05-24 All chapters changed CWE and MS 0.4 Draft 2014-05-29 All chapters changed CWE and MS 0.5 Review 2014-05-30 All chapters changed CWE and MS 0.6 Review 2014-06-01 All chapters changed CWE and MS 0.7 Review 2014-06-01 All chapters changed CWE and MS 1.0 Final 2013-06-02 All chapters changed CWE and MS I Version 0.7 Chi Winth Ea Multi-purpose Embedded Communication Gateway: Morten Sørbø System Design and Testbed Implementation Preface This dissertation was written by ICT masterstudents at the University of Agder in Grimstad, Norway, from January 2014 to June 2014. The thesis has been supervised by Postdoctoral researcher Lei Jiao, University of Agder. With weekly meetings, the process has been continuously smooth as there has always been enough work to do. The equipment used during the thesis is financed by the University of Agder. Some was already available at the University, but most of the devices had to be aquired by the writers. As time was of the essence, it has been important to choose equipment that was easily available to borrow or purchase. II Version 0.7 Chi Winth Ea Multi-purpose Embedded Communication Gateway: Morten Sørbø System Design and Testbed Implementation Acknowledgements We would like to express our gratitude towards Dr. Lei Jiao for his invaluable guidance during this dissertation. It has been a pleasure having him as our supervisor as his input during our time together steered us towards the completion of our work. He has been very gracious with his time, and made us feel prioritized along the whole process. Grimstad June, 2014 Chi Winth Ea and Morten Sørbø III Version 0.7 Chi Winth Ea Multi-purpose Embedded Communication Gateway: Morten Sørbø System Design and Testbed Implementation Abstract This dissertation revolves around developing a multi-purpose embedded communication gateway. The gateway is equipped with multiple communication interfaces including Ethernet, Bluetooth, WiFi, Zigbee, LTE, and it can be configured and utilized for many purposes, such as a failover of an Ethernet cable via 4G in order to maintain the network connectivity. Raspberry Pi circuit board and the operating system Raspbian are selected as the hardware and the software platforms respectively. Different communication interfaces are coordinated by the Raspberry Pi and are configured via Linux scripts according to various use cases. Furthermore, a hardware watchdog is adopted to enhance the availability of system. In addition, the system is encapsulated into a box to increase its portability. The system is validated and evaluated through rigorous test-bed experiments. Experiment results indicate that the developed router works smoothly and reliably in environments with little electrical disturbances. IV Version 0.7 Chi Winth Ea Multi-purpose Embedded Communication Gateway: Morten Sørbø System Design and Testbed Implementation Contents 1 Introduction ................................................................................................................................... 12 1.1 Background ............................................................................................................................ 13 1.2 Problem Statement ............................................................................................................... 13 1.3 Problem Solution ................................................................................................................... 13 1.4 Organization of the Dissertation ........................................................................................... 15 2 Existing Work ................................................................................................................................. 16 2.1 Commercial Products ............................................................................................................ 16 2.2 Research Studies ................................................................................................................... 17 2.2.1 Network Failover ........................................................................................................... 17 2.2.2 Data Syncronization Technologies ................................................................................ 17 2.2.3 Watchdog as a Reliability Improvement ....................................................................... 18 3 System Design ............................................................................................................................... 20 3.1 System Overview ................................................................................................................... 20 3.2 Overview of Hardware .......................................................................................................... 21 3.2.1 Main Computer Board – Raspberry Pi ........................................................................... 22 3.2.2 Watchdog – Arduino...................................................................................................... 23 3.3 Overview of Software ............................................................................................................ 23 3.3.1 Operating System for Raspberry Pi ............................................................................... 24 3.4 Overview of Interfaces .......................................................................................................... 25 3.4.1 Technologies .................................................................................................................. 25 3.4.2 Communication Dongles ............................................................................................... 27 4 Implementation ............................................................................................................................. 28 4.1 Software Installation and Interface Initialization .................................................................. 28 4.1.1 Operation System Installation ....................................................................................... 28 4.1.2 Mobile Broadband Software ......................................................................................... 31 V Version 0.7 Chi Winth Ea Multi-purpose Embedded Communication Gateway: Morten Sørbø System Design and Testbed Implementation 4.1.3 Wi-Fi Access Point ......................................................................................................... 33 4.1.4 Ethernet ......................................................................................................................... 35 4.1.5 Routing .......................................................................................................................... 35 4.1.6 E-mail ............................................................................................................................. 39 4.1.7 Bluetooth ....................................................................................................................... 39 4.1.8 ZigBee ............................................................................................................................ 41 4.1.9 Kernel Compilation ........................................................................................................ 43 4.1.10 SD-Card Protection ........................................................................................................ 45 4.1.11 MySQL Installation Proposal.......................................................................................... 47 4.2 Mobile Broadband Failover ................................................................................................... 49 4.2.1 The Initialization of the Script ....................................................................................... 51 4.2.2 While Loop When There is Internet Connectivity ......................................................... 52 4.2.3 While Loop When There is Only Local Network Access ................................................ 54 4.2.4 While Loop When There is No Network Access ............................................................ 55 4.3 The Watchdog ....................................................................................................................... 57 4.3.1 Internal Watchdog ......................................................................................................... 57 4.3.2 External Watchdog ........................................................................................................ 59 4.4 Other Reliability Measures .................................................................................................... 63 4.5 Physical Implementation ......................................................................................................