Reliable Data Delivery over Wireless Sensor Networks

Abstract: In this thesis we present ReDaR, a software and hardware environment for reliable data retrieval from multiple remotely located wireless sensor networks (WSNs). The software is programmed in Java and NesC over TinyOS, and allows for direct interaction with individual sensors using a graphical user interface running on a remote client. The hardware platform includes a WSN deployed with Telos wireless sensors. ReDaR implements a control algorithm over a real WSN, which allows to keep under control the overhead communication bandwidth between the sensors and the remote client. Specifically, we implement a control algorithm based on the extremum seeking control theory, which enables an adaptive forward error correction mechanism to ensure reliable real-time data retrieval. The amount of redundancy is controlled via a switching controller that uses a feedforward and a feedback mechanism. The switching controller ensures an optimal trade-off between maximizing the bandwidth and maximizing the quality of service. Experiments performed in our environment confirm theoretical results about performance of the controller, i.e. the feedback mechanism provides a robust controller that finds the optimum without model reliance, while the feed forward one improves the transient behavior.