Small world for dynamic wireless cyber-physical systems: Dissertation

Today, industries and consumer markets are increasingly using services exposed from wireless sensor and actuator networks. Such systems are here referred to as cyber-physical machine-to-machine systems. These systems rely on the capability to communicate, compute, monitor and control by using information. The motivation for the present research arises from problems detected in the remote interaction with embedded devices over dynamic wireless networks in such systems. The problems are caused by the heterogeneity of devices, networks and operating environments, mobility, dynamic presence, security demands of the owners and of use, multiple radios, unreliability, dynamic topologies, and changes happening in the system. The approach selected in this research to address these problems is based on the application of the small-world paradigm to cyber-physical systems. The small-world paradigm is based on the observation that people are often linked in a successful social communication chain by, on average, six intermediate steps. In the present study, it is assumed that the concept of small world can be expanded to also cover communication with wireless embedded devices in cyber-physical systems context. In addition, it is expected that creation of wireless short-cuts can, in accordance with the small-world paradigm, improve the scalability and efficiency of dynamic wireless networking. The main contributions of this research are the technical enablers referred to as dynamic communication spaces, dynamic M2M service spaces, configuration and remote use of services, communication overlay, access systems selection, integrated mobility, secure ad hoc networking, situated opportunistic communication, hierarchical networking for small-world networks, and short-cuts for network optimization. Each of the provided technical enablers contributes towards making remote interaction with embedded devices over dynamic wireless networks possible. The enablers have been evaluated as separate technical methods and means by means of experiments and/or simulations. On the basis of the analysis and synthesis, it was established that they work well as separate building blocks and that they can be combined to expand the concept of small world to also cover communication with embedded devices. Furthermore, it was established that creation of wireless short-cuts can, in accordance with the small-world concept, improve the scalability and efficiency of dynamic wireless networking. In addition, weak links were observed to be essential in the small-world neighbour discovery process. In sum, the evaluation results indicate that the provided enablers help the remote interaction with embedded devices and promote the application of the smallworld concept to dynamic wireless cyber-physical systems.