Localization Systems Using Passive UHF RFID

Since gathering spatial information of objects often provides a large number of extended functions in RFID based applications, many different localization systems have been developed in recent years. Determining and estimating the physical location of tagged objects in an interrogating area is known as localization. In this paper, we study properties of passive UHF RFID systems such as the relationship between distance and RSSI (received signal strength indictor), performance variations among the same type of passive tags, and readabilities of tags. We propose a received signal strength based localization algorithm using passive UHF RFID system. The localization uses the k-nearest neighbor algorithm to estimate the physical position of the target tag. To improve the accuracy of the passive tag attached object location, the properties and characteristics are applied to the localization algorithm. According to the analysis of experimentation, our proposed approach shows over 34% improvement compared with the k-nearest neighbor algorithm with the use of single reader and a single antenna, and 13 reference tags.