Energy packet network with negligible service time: a modelling and performance analysis approach to wireless sensor networks

Abstract

Autonomous self-organising systems have gained much attention to manage complex tasks without any human interaction. Similarly, simpler systems are also required for the applications of Internet of Things, such as smart home services, wearables, smart cities and connected health systems. These simpler systems provide autonomous standalone devices for remote sensing, processing and transmission of information. However, such devices may not have a reliable connections to power mains or may not be convenient for regular battery replacements. Therefore, local energy capturing from ambient intermittent sources such as vibration, electromagnetic waves, heat or light through harvesting could be of great interest for such devices. This thesis researches mathematical modelling and performance analysis of such autonomous digital devices operating with energy harvesting from intermittent sources. The approach used in this research is based on the Energy Packet Network paradigm where the arrivals of data and energy at devices are considered as discrete random processes. The devices operate by consuming harvested energy in a discrete manner in order to process, store and transmit data (wired or wireless) in a negligible time interval, such that the operation or the workload of the devices is also modelled as a discrete random process. Probability models based on random walks and Markov chains are investigated in this study to predict effective rates at which such devices operate well for different energy consumption scenarios, and to obtain closed-form formulas for stationary probability distributions and to make further analysis on the other quantities of interest. Consequently, a “product form solution” of a cascade network of N nodes where state transitions involve simultaneous state changes in multiple nodes, due to data packets that flow through several nodes consuming energy packets is proposed. A modelling approach to evaluate the effect of several battery attacks on such devices is studied. Finally, optimum placement of wireless nodes into a region where there is a spatial continuous distribution of energy and data traffic is presented for different transmission schemes, and optimisation objectives.