RFID-based centralized cooperative localization in indoor environments

We demonstrate the effectiveness of a cooperative scheme to improve the positioning accuracy of four users moving in a building, by using the received signal strength (RSS) measurements from a number of known location RFID tags (anchors) and combining it with RSS measurements of mobile tags carried by themselves. The method is based on a centralized particle filter approach over the joint state of all users. Due to a relatively small number of anchor nodes (7 tags for an area of 1600 M-2), individual localization is not very accurate (median error of 6.2 m), but this improves to 5.1 m when cooperative measurements are taken into account. When PDR estimates of user displacement are incorporated to the particle filter, the median positioning error is further decreased to 4.0 m (individual localization) and 3.5 m (cooperative localization).