A Modular and Open Software and Hardware Architecture for Internet of Things Sensor Networks
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UNIVERSITY OF SOUTHAMPTON FACULTY OF ENGINEERING AND PHYSICAL SCIENCES A Modular and Open Software and Hardware Architecture for Internet of Things Sensor Networks by Mihaela Apetroaie-Cristea Supervisor: Prof. Simon J. Cox and Dr. Steven J.J. Ossont June 25, 2020 iii UNIVERSITY OF SOUTHAMPTON ABSTRACT FACULTY OF ENGINEERING AND PHYSICAL SCIENCES A Modular and Open Software and Hardware Architecture for Internet of Things Sensor Networks by Mihaela Apetroaie-Cristea We are experiencing a new industrial revolution, a cyber-physical systems revolution. The Internet of Things (IoT) is at the core of this development, and it is changing the way we perceive the world around us, impacting both business and technology. Smart cars, smart thermostats, home automation hubs, smart lighting, and smart weather stations are common technologies met in most cities and households. The number of these devices is going to increase even more, and it is predicted to reach billions over the next few years. Although the IoT technology has reached maturity, we are still unprepared for the large number of devices predicted to reach the world in the near future. Managing high numbers of IoT devices requires stable infrastructures for deployment and manage- ment. It also requires creating sustainable infrastructures to minimise the impact on the environment. In this thesis, we hypothesise that using flexible, open, modular, and reconfigurable hardware and software architectures at the base of smart city infrastructure can increase device longevity and minimise device management complexity at scale, while promot- ing sustainable development. The main contributions are: (1) identification of design requirements for building the next generation IoT device (2) reference architecture for flexible, modular IoT devices, (3) a novel, modular, open-source sensor board for build- ing plug-and-play smart devices, allowing for complete removal/replacement of sensors and computing module, (4) a novel, modular, open-source software architecture, includ- ing: minimal Operating System (OS), over the air (OTA) updates, containerisation and remote device management, and (5) demonstration using a real-life application of en- vironmental monitoring. The reference architecture presented in this thesis provides a robust, persistent, and reliable long-term solution for IoT deployements that addresses concerns regarding the negative impact of IoT on long term sustainable development. Contents Acknowledgements xi Declaration of Authorship xiii 1 Introduction1 1.1 Thesis structure.................................3 2 The Internet of Things in our lives7 2.1 Towards ubiquitous computing........................8 2.1.1 Sustainability..............................8 2.1.2 Internet of Things to address global goals..............8 2.1.3 Internet of Things in our cities....................9 2.2 Internet of Things hardware technologies................... 12 2.2.1 Single Board Computers........................ 12 2.2.2 Sensors................................. 12 2.3 Enabling technologies............................. 14 2.3.1 Open Sensors Platforms........................ 14 2.3.2 Scalability................................ 15 2.3.3 Networking............................... 18 2.3.4 Operating Systems and Unikernels.................. 19 2.3.5 Over the air updates.......................... 22 2.3.6 Containerisation............................ 24 2.4 Internet of Things applications........................ 26 2.4.1 Air Quality monitoring......................... 26 2.4.2 Plug and Play platforms........................ 27 2.5 Research Questions and Objectives...................... 29 3 Indoor positioning system 33 3.1 Indoor localisation system based on low-cost commodity hardware.... 34 3.1.1 Introduction............................... 34 3.1.2 Design of the Indoor Localisation System.............. 35 3.1.3 Preliminary Testing.......................... 36 3.1.3.1 Methods........................... 36 3.1.3.2 Results............................ 37 3.2 Further assessment of the system performance................ 38 3.2.1 Methods................................. 39 3.2.2 Discussion and analysis of the results................. 39 3.3 Conclusions and future work.......................... 45 v vi CONTENTS 4 Generic IoT device for an environmental monitoring use case 49 4.1 Development.................................. 49 4.2 Theoretical use case - Southampton Smart City............... 50 4.3 Air quality monitoring............................. 52 4.4 Preliminary testing............................... 53 4.4.1 Implementation............................. 53 4.4.2 Data................................... 54 4.4.3 Security and Privacy.......................... 54 4.4.4 Outreach................................ 57 4.5 Lessons learned................................ 58 5 Hardware architecture 61 5.1 Introduction................................... 61 5.2 Motivation.................................... 61 5.3 Proposed Solution............................... 62 5.4 Environmental monitoring example...................... 64 5.5 Face validation - results and conclusions................... 65 5.6 Known issues and limitations......................... 69 6 Software architecture 71 6.1 Introduction................................... 71 6.2 Requirements.................................. 73 6.3 Operating Systems............................... 73 6.4 Remote device management.......................... 75 6.5 Over the air updates.............................. 75 6.5.1 OSTree................................. 76 6.6 Containerisation................................ 78 6.6.1 Applications in containers....................... 79 6.7 Server-side requirements and considerations................. 79 6.8 Power...................................... 80 6.9 Implementation details - other technologies................. 81 6.10 Face validation - results and discussion.................... 82 6.10.1 Implementation details......................... 82 6.10.2 Experiments............................... 83 6.10.3 Security and privacy.......................... 86 6.10.4 Known issues and limitations..................... 87 7 Conclusions 91 8 Future work 95 A PiSEB v1.0 Eagle Schematics 99 B PiSEB v2.0 Eagle Schematics 109 References 119 List of Figures 1.1 Hype Cycle for Internet of Things [148]....................2 1.2 IoT continous development..........................3 1.3 Proposed hardware and software modular architecture, where S represents a sensor.....................................5 2.1 The United Nations Global Goals adopted in 2015 [54]...........8 2.2 BalenaOS Architecture............................. 21 2.3 Containarisation software architecture.................... 24 2.4 Sandboxing software architecture....................... 25 3.1 Locator node.................................. 35 3.2 Section of the office area............................ 37 3.3 Testing area layout............................... 37 3.4 Graph illustrating the error variation at 17 measurement points....... 38 3.5 The error variation when three locator nodes have been considered.... 38 3.6 Variation of the position estimation errors at the measurement points for the indoors experiment............................. 40 3.7 Variation of the position estimation errors at the measurement points for the outdoors experiment............................. 40 3.8 Variation of the error with ideal solution scoring for the indoor measurements 41 3.9 Variation of the error with ideal solution scoring for the park measurements 42 3.10 Represenation of the solution interval as the intersection between the rings to include the signal strength noise parameter ∆ .............. 43 3.11 Radiation pattern of the omnidirectional, high-gain antenna used for this project [143].................................. 44 4.1 Map of Southampton.............................. 51 4.2 Device architecture for the preliminary test................. 53 4.3 Preliminary test SO2 and NO2 data...................... 55 4.4 Preliminary test PM2.5 data.......................... 55 4.5 Preliminary test temperature data....................... 56 4.6 Preliminary test pressure data......................... 56 4.7 Example of the charts used in the preliminary testing............ 58 5.1 Reference hardware modular architecture, where S represents a sensor.. 63 5.2 PiSEB development board [12] designed as part of this research, where the continous line delimitates the microcontroller (pycom) and SBC (Rasp- berry Pi) interfaces............................... 63 5.3 The hardware used for the environmental sensor prototype......... 65 vii viii LIST OF FIGURES 5.4 Reference hardware modular architecture, where S represents a sensor.. 67 6.1 Reference modular architecture showing the main technologies used for our software implementation.......................... 73 List of Tables 2.1 Gas sensors costs and performance metrics.................. 15 3.1 Cost and accuracy of top indoor positioning systems on the market.... 35 3.2 Price of locator node............................. 35 3.3 Requirements.................................. 47 4.1 The sensors chosen for the first version of the generic IoT device..... 50 4.2 Methods for achieving the design requirements - customisation, expansion, maintenance and accessibiliy- hw represents hardware and sw represents software..................................... 60 5.1 The sensors chosen for the final version of the generic IoT device..... 66 5.2 Hardware face validation results.......................