The advent of GPS has redefined the need of a positioning system in today*#8217;s ubiquitous computing world. While GPS works satisfactorily and is quite a norm in an outdoor environment, it fails to work indoors due to the inherent complexity of an indoor environment. There is an ever increasing need to develop an indoor positioning system and a lot of research has been done to solve the problem of indoor localization. These solutions differ on the basis of cost, dependency on environment, line of sight requirements and so on.
Passive RFID (Radio Frequency Identification) tags pose an interesting solution to the problem of indoor localization, given the ease of deployment and the cost effective infrastructure. It is less expensive to tag items with RFID tags, than to attach them with sensor nodes. In this thesis, the problem of using the RFID technology for two dimensional indoor localization is studied. A relatively inexpensive technique requiring just one RFID reader and multiple passive RFID tags is adopted. The idea is to use multilateration among the passive tags to solve the problem of localization. A ranging technique is developed to establish a relationship between signal strength and distance. The concept of Received Signal Strength calibration is used to develop the ranging technique, and to account for the effects of dynamic environmental conditions on localization. Finally, an error map matching technique is employed to counter the errors in localization.