A Fuzzy Set-Based Approach to Range-Free Localization in Wireless Sensor Networks

Localization in Wireless Sensor Networks (WSNs) refers to the ability of determining the positions of sensor nodes, with an acceptable accuracy, based on known positions of several anchor nodes. Among the plethora of possible localization schemes, the Received Signal Strength (RSS) based range-free localization techniques have attracted significant research interest for their simplicity and low cost. However, these approaches suffer from significant estimation errors due to low accuracy of RSS measurements influenced by irregular radio propagation. In order to tackle the problem of RSS uncertainty, in this work we propose a fuzzy set-based localization method as an enhancement of the ring-overlapping scheme [1]. In the proposed method, first we use a fuzzy membership function based on RSS measurements to generate fuzzy sets of rings that constrain sensor node position with respect to each anchor. Then we generate fuzzy set of regions by intersecting rings from different ring sets. Finally, we employ weighted centroid method on the fuzzy set of regions to localize the node. The results obtained from simulations demonstrate that our solution improve localization accuracy in the presence of radio irregularity, but even for the case without radio irregularity.