Using Virtual Reference Tags to Improve the Accuracy of Active RFID-Based Positioning Systems

Up to now, different indoor positioning algorithms based on Active RFID technology have been presented. These algorithms use the concept of reference tags to locate tracking tags that are attached to objects. Experimental results have shown that the increase of reference tags caused the increase of positioning accuracy. However if the number of these reference tags exceeds a limit two problems can arise. The first problem is the increase of multipath propagation and signal interference. The second problem is the increase of cost. In order to improve the performance of indoor environment this paper presents a new method to estimate the tracking tags' location based on virtual reference tags instead of increasing the number of real reference tags. In this method after calculating RSSI of each virtual reference tag by its surrounding real reference tags RSSI, sensing area is divided into several sections and tracking tags location is calculated by real or virtual reference tags which are in section that the objects has the highest probability to be enclosed within. Experimental results show that our purposed algorithm considerably reduced error estimation of previous algorithms. In comparison with LANDMARC and VIRE approach, we reduced average estimation error by about 70 percent and 10 percent respectively.