Tag Cardinality Estimation Using Expectation-Maximization in ALOHA-Based RFID Systems With Capture Effect and Detection Error

Tag cardinality estimation is one of the most crucial issues in radio frequency identification technology. The issue, however, usually faces with challenges in wireless fading environments due to the presence of the so-called capture effect (CE) and detection error (DE). The aim of this letter is to provide an efficient and accurate estimation method to cope with the CE and DE using expectation-maximization algorithm and the standard Aloha-based protocol. We show that the proposed method gives more accurate estimates than a conventional one. Thanks to this fact, the Aloha frame size used for the tag identification process can also be optimally selected so that the identification efficiency can be improved. Computer simulations are presented to confirm the merit of the proposed method.