| Summary: | Wireless sensor networks (WSNs) are characterized by limited amount of energy supply
at sensor nodes. Hence, energy efficiency is an important issue in system design and operation of WSNs.
In this work we focus on solving the energy efficiency problems of data gathering processes
in WSNs. We first address this problem on a macroscopic level by investigating the efficiency of data gathering trees when data sent by different sensors are correlated. Such
correlation aware data gathering strategies typically shift the aggregation structure from a
default shortest-path tree (SPT) to a steiner minimum tree (SMT) in order to achieve the
required efficiency.
We study the energy efficiency of correlation aware data aggregation trees under various
sensor network conditions and the tradeoffs involved in using them. Comprehensive simulation
results as well as inferences and theoretical analysis of those results are presented in the thesis.
Based on the insights gained through the investigation, we propose a simple, scalable
and distributed correlation aware aggregation structure that achieves good energy performance
across a wide range of sensor network configurations, and at the same time addresses
the practical challenges of establishing a correlation aware data aggregation structure in
resource-constrained WSNs.
On a microscopic level, we propose a novel communication strategy called Communication through Silence (CtS) to achieve energy-efficient data gathering without significant
degradation on overall throughput in WSNs. The proposed scheme primarily uses time, along with a minimal amount of energy to deliver information among sensors. CtS can be used to replace the conventional energy-based transmissions between each pair of sensor nodes during a data gathering process. We analyze in detail the primary energy-throughput tradeoff inherent in this approach as well as other challenges related to the realization of the
proposed communication strategy. Finally, we propose a practical realization of CtS strategy
that includes radio technology, MAC layer, and higher layer solutions. Performance evaluation results prove that this solution effectively realizes the CtS strategy in a WSN setting, at the same time achieves considerable energy savings compared to conventional communication strategies.
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