Reliable Architecture for Future Smart Communities.

Smart communities of the future require a reliable communications infrastructure, which is able to provide seamless connectivity and at the same time is resistant to failures and secured against hacker attacks. A new subset of Internet of Things (IoT)
technologies, called Low-Power Wide Area Network (LP-WAN), has been developed to address such needs. However, the current design of the most prominent LP-WAN technologies is not fully ready to live up to the smart community expectations. This
thesis describes the efforts that evaluate the coverage, failure-safety and security of the LP-WAN protocols: Narrowband Internet of Things (NB-IoT), LTE for MachineType Communications (LTE-M), Long Range Wide Area Network (LoRaWAN) and Sigfox, and explores the possibilities to enhance their capabilities in those aspects. Particularly, in this work multiple coverage field trials and measurement campaigns were conducted in an outdoor and an underground deep-indoor environment. As a result, a new empirical dataset, as well as deep-indoor channel predictor models, were derived. Moreover, a lightweight Radio Access Network (RAN) enhancement providing evolved node-B (eNB) failure tolerance in Cellular Internet of Things (CIoT) networks was proposed. Furthermore, security breaches of NB-IoT, LoRaWAN and Sigfox were identified. A new research direction of Sustainable Security for Internet of Things (SSIoT) was introduced and Group Object Security for Constrained RESTful Environments (OSCORE) security protocol for constrained devices was implemented and experimentally evaluated. The outcome of the research work can be summarised as follows: 1) satisfactory LP-WAN coverage could be observed in all the measured scenarios. Environmental feature engineering based on empirical data can be helpful to identify new factors influencing the radio signal attenuation and, consequently, derive new and more accurate path-loss predictors. 2) A Device-to-Device (D2D)-based scheme for CIoT, which introduces eNB failure-tolerance is considered a promising way of increasing the robustness of the IoT system at a minimal resource cost; 3) NB-IoT, LoRaWAN and Sigfox protocols have shown their security weaknesses, which ought to be continuously analysed and addressed in the standardisation process. Future IoT security works should follow the path of Sustainable Security for Internet of Things (SSIoT), and an example of a robust, but lightweight and sustainable security solution for IoT application-layer is Group OSCORE protocol, which was experimentally verified.