Indoor localization technique using passive RFID tags

In this paper, radio frequency identification (RFID) technology is used for localization system. The location of a RFID reader is estimated based on the known locations of RFID tags using the UHF band RFID system. The new location estimation method based on the angulation technique is proposed to determine the reader location in real time. For angulation technique, the RFID reader is held on the camera tripod and it is considered as the target to be localized. The passive tags are attached at the known location and considered as the references. In this case, the RFID tags are put in the horizontal straight line on different sides on the walls (around the corner). The required parameter is the angle between the tag and the reader. In this paper, a compass is employed to measure the angle between the tag and the reader. Therefore, at least two angles are needed and further used to calculate the true location of the reader by using two formulated linear equations. This technique is verified using the experiment data. Two experiments are conducted with two different distances between tags and reader, i.e. 100 cm and 150 cm. The experiment results of location estimation show that the average location estimation error is around 16 cm for the 100 cm distance and around 20 cm for the 150 cm distance. This implies that the proposed method is satisfied to use for indoor applications.