Context-aware applications is not just a vision. Advances in wireless communications and mobile capabilities have revolutionized the way services are brought to users, i.e. adapted to their context. Location is a key attribute of the term context and thus, an accurate location determination system is of paramount importance. RFID (Radio Frequency IDentification) is an emerging technology and recently has been explored for its applicability in location sensing systems. In this paper, we focus on an RFID-based localization approach in an indoor multi-user environment and model its most adverse implicating factors, that is collisions among its main components and interference from indoor characteristics. Extensive simulations are conducted to characterize and evaluate the performance behavior of the proposed scheme in environments with different levels of severity