Fuzzy ring-overlapping range-free (FRORF) localization method for wireless sensor networks

The sensor node localization with an acceptable accuracy is a fundamental and important problem for location-aware applications of Wireless Sensor Networks (WSNs). Among numerous localization schemes proposed specifically for WSNs, the Received Signal Strength (RSS) based range-free localization techniques have attracted considerable research interest for their simplicity and low cost. However, these techniques suffer from significant estimation errors due to low accuracy of RSS measurements influenced by irregular radio propagation. In order to cope with the problem of RSS uncertainty, in this paper we propose a fuzzy set-based localization method, called Fuzzy Ring Overlapping Range Free (FROFR) localization. Similar to other area-based localization schemes, FRORF relies on beacon signals broadcasted by anchors to isolate a region of the localization space where the sensor node most probably resides. As an extension to the concept of ring-overlapping localization, FRORF first represents overlapping rings as fuzzy sets with ambiguous boundaries in contrast to fixed intervals of RSS values, and then generates fuzzy set of regions by intersecting rings from different fuzzy ring sets. The degrees of sensor node membership to regions in the fuzzy set of regions are used to determine the location estimate. The results obtained from simulations demonstrate that our solution improve localization accuracy in the presence of radio irregularity, and even for the case without radio irregularity.