Resolving Collision in EPCglobal Class-1 Gen-2 System by Utilizing the Preamble

The collision resolution mechanism is a key factor for successful communication in dense Radio-Frequency Identification (RFID) systems. One of such collision resolution mechanisms is the ALOHA protocol used in the EPCglobal Class-1 Gen-2 standard (EPCglobal). The success of the ALOHA-based protocols in RFID systems depends on the estimation of the number of tags in the electromagnetic field of an interrogator. The majority of the proposed optimization methods of the ALOHA-based protocols focus mainly on the estimation of the number of tags based on past slot results. Only few of the proposed methods try to determine the exact number of tags that involve an analysis of the received signal. One such method is the Radar Cross Section (RCS) method. We will show that RCS is not appropriate for RFID systems that include channel filtering as in the case of the EPCglobal standard. As a replacement for the RCS method, we propose a new anti-collision method to improve the anti-collision mechanism based on the utilization of the frequency analysis of the preamble. We will demonstrate that the method improves the existing anti-collision algorithm used in the EPCglobal and enhances the capture effect capability.