Performance Evaluation of Missing-Tag Algorithms in CDMA-based RFID Systems

This paper investigates designing efficient communication schemes to monitor and to identify missing tags in CDMA-based RFID systems in a short period of time. In our considered systems, each CDMA tag is assigned with an unique Gold code, and randomly responds to the RFID reader thanks to the Frame Slotted ALOHA-based protocol. The de-correlating detector is implemented at the reader to eliminate impacts of Multiple Access Interference (MAI). We, then, propose and analyze two protocols, namely CDMA-based Two-Phase Protocol (CTPP) and CDMA-based Two-Phase Protocol with Tag Removal (CTPP/TR), in which optimal protocol parameters are determined to minimize the execution time. Computer simulations are performed to validate the theoretical analysis considering effects of fading phenomenon. In the numerical results, we evaluate the performance of the missing-tag protocols with different system parameters. From the results, adequate system settings are selected to fulfill requirements of the so-called false alarm rate and the false detection rate. We also confirm the superiority of the proposed protocols in comparison with conventional ones.