Synchronization of Wireless Sensor Networks

Abstract

Wireless sensor networks of the type discussed in this MSc project play a crucial role in many envisionings of the Internet of Things, a trend that is thought to play a major role in the technological innovations of the near future. These wireless, ad-hoc, scalable mesh networks provide the infrastructure for numerous sensing and control applications. A key requirement for such networks is energy efficiency. Synchronization of nodes can significantly improve energy efficiency by enabling a tighter communication schedule. In this MSc project an improved synchronization algorithm for an existing MAC protocol is developed. After establishing a clock model and surveying the literature for existing algorithms, the synchronization problem is modelled from a control theoretic viewpoint. It is shown that the synchronization problem closely resembles the consensus problem, which is extensively covered in literature. This insight is used to prove stability of a class of synchronization algorithms -- including the existing algorithm -- under requirements on the communication topology that are easily satisfied. A set of improved algorithms is developed, and their performance is assessed in simulations. The best performers were tested experimentally on networks with up to 300 nodes. In conclusion, we have been able to create a substantial improvement over the existing synchronization algorithm, attaining a higher throughput and longer network lifetime. Experiments have shown however, that very large networks (>150 nodes) are not adequately described by our models and can display unexpected dynamics.