Lessons learned on device free localization with single and multi channel mode

Indoor localization applications that involve Wireless Sensor Networks (WSNs) identify the target position by measuring the Received Signal Strength (RSS), the Time of Arrival (ToA), the Time Difference of Arrival (TDoA) or the Angle of Arrival (AoA). Of these, the most promising for low-cost applications are those based on measures of the RSS, which exploit the relationship between RSS and the distance, or more reliably the relation between the multi-path interference (shadowing) and the position of the target. These methods work with WSNs based on Wi-Fi, Bluetooth and ZigBee sensor technologies. In this paper we concentrate on device-free RSS-based indoor localization methods. These methods, which have generated much research interest in the last few years, are now starting to hit the market. Specifically, the purpose of this paper is to assess the performance improvements of a Variance-based Radio Tomographic Imaging technique, when scanning various radio channels with respect to using only one, the latter being the “minimum introduced interference” option. Moreover, in this paper we will discuss in which application scenario the multi-channel scanning technique is usable and appropriate. The experimental data used for target localization are captured by wireless sensors deployed in the localization area and the localization error metrics include the mean square error and percentiles of the error distribution. Specifically, we aim to study the localization error reduction obtained by using multiple ZigBee channels, with respect to using a single channel.