RFID estimation functions overview

Radio Frequency Identification (RFID) is a pervasive computing technology with purpose is to identify, track and trace objects or persons. The identification is carried by a so called tag attached to the targeted item. The former contains the unique identification serial number (UISN) which will be `transmitted´ to a Reader. When more than one tag are in the interrogation area of the base station, this situation is characterized by a simultaneous tag response which my lead to a collision. This phenomenon is traduced by garbled data at the reader side; as a result the identification process is not achieved. In order to resolve this problem, the use of anti-collision Algorithm is required. Although this problem was well studied in the literature for classical networking, it still is looking for enhancement in the RFID field, due to the particularity of RFID tag (lack of memory, energy and computational capabilities). This work aims to propose a quick overview of cardinality estimation functions used for RFID anti-collision algorithms. Estimation phase is highly required to adapt reading cycles with the number of tags in the base station´s interrogation area.