Review on UHF RFID Localization Methods

With the wide spread of the Internet of Things (IoT), wireless localization technology has provided various location-based applications and services. Radio frequency identification (RFID) has been widely used in objects' identification and tracking. Combining with its excellent identification ability, RFID is also a promising technique for indoor localization. This paper provides the state-of-the-art of UHF RFID localization and gives an introduction of methods and applications. The major methods of UHF RFID localization have two types: 1) range-based and 2) range-free, reported in previous literature. The range-based methods obtain the distance or angle between the antenna and tag utilizing the received signal strength indicator (RSSI), time information or signal phase and estimate tag location further combining the scheme geometrical characteristics. The methods based on fingerprinting and non-fingerprinting are mainly discussed in the range-free domain. Finally, a comparative study of these surveyed works are presented and concluded with a future trend.