Use of frequency diversity to improve the performance of RSSI-based distance measurements

In several fields of application of wireless sensors networks (WSNs) the ability of estimating the position of a node with respect to a reference coordinate is a key feature. The most of the WSN applications involve indoor environments and low costs requirements, so the Global Position System cannot always assure a reliable operating and cheap solution. As a consequence, other methods have to be considered for nodes locating, among all, the most widespread methods are based on Received Signal Strength Indicator (RSSI) measurements. The main advantage of this method is that it does not require additional hardware since the measurement of RSSI is often built-in in radio chipsets for the most common standards in use for a WSN (Bluetooth, Wi-Fi, ZigBee). However, solutions based on RSSI measurements suffer of high uncertainty due to several phenomena as high variability of RSSI measurements, external interferences and multipath to cite a few. In this paper the influence of the multipath is investigated and the effects of different processing techniques for multipath mitigating, based on the employment of frequency diversity, are analyzed in simulation environment and in real scenarios.