Considering Link Qualities in Fault-Tolerant Aggregation in Wireless Sensor Networks

The goal of Wireless Sensor Networks is to extract useful global information from individual sensor readings, which are typically collected and aggregated over a spanning tree. However, the spanning tree structure is not robust against communication errors; a low-quality (i.e., high-error-rate) wireless link close to the tree root may result in a high rate of global information loss. Therefore, many schemes have been proposed to achieve fault-tolerant aggregation. Intuitively, using timely link-quality information, which is gathered by continuous monitoring and error-rate measurement of network links, improves the performance of fault-tolerant aggregation schemes. In this paper, we show that this intuition is not always true. In particular, we show that using link-quality information in an intuitive but wrong way results in degraded performance in some schemes, and therefore, care should be taken in using link-quality information. We also show that some schemes make better usage of link-quality information than others, and some schemes are more robust to errors in link-quality estimation than others. We support our findings by an extensive simulation study, and we focus on the (more general) class of fault-tolerant duplicate-sensitive aggregation schemes.