The Applicability of RFID for Indoor Localization

Although RFID has a relatively long history of more than 50 years in the field of wireless communications, only the last decade it has received a considerable attention for becoming a useful general purpose technology. Actually, RFID was initially developed as an automatic identification system consisting of two basic component types, a reader and a tag (Want, 2006). The reader is able to read the IDs of tags in its vicinity by running a simple link-layer protocol over the wireless channel. RFID tags can be either active or passive depending on whether they are powered by battery or not, respectively. Passive tags are prevalent in supply chain management as they do not need a battery to operate. This makes their lifetime large and cost negligible. The low cost of passive tags, the non-LOS requirement, the simultaneous reading of multiple tags and the reduced sensitivity regarding user orientation motivated the academia and industry for exploring its potentials in more intelligent applications Baudin & Rao (2005). This chapter studies whether an RFID deployment can be applied for the purpose of indoor localization. It is widely accepted that location awareness is an indispensable component of the future ubiquitous and mobile networks and therefore efficient location systems are mandatory for the success of the upcoming era of pervasive computing. However, while determining the location of objects in outdoor environments has been extensively studied and addressed with technologies such as the Global Positioning System (GPS) (Wellenhoff et al., 1997), the localization problem for indoor radio propagation environments is recognized to be very challenging, mainly due to the presence of severemulti-path and shadow fading. The key properties of RFID motivated the research over RFID-based positioning schemes. Correlating tag IDs with their location coordinates is the principle concept for their realization. Though RFID offers promising benefits for accurate and fast tracking, there are some technology challenges that need to be addressed and overcome in order to fully exploit its potential. Indeed, the main shortcoming of RFID is considered the interference problem among its components, mainly due to the limited capabilities of the passive tags and the inability of communication between readers (GP & SW, 2008). There are three main types of RFID interference. The first one is due to the responses of multiple tags to a single reader’s query, the second is related to the queries of multiple readers to a single tag and finally, the third is due to the low signal power of weak tag responses compared to the stronger neighbor readers’ transmissions. The first type affects the time response of the system, whereas the other two reduce the positioning accuracy. In addition, interference from non-conductive materials such as metal or glass imposes one more concern regarding the appropriateness of RFID for widespread deployment. 11