An extensive study of slotted Aloha-based RFID anti-collision protocols

Radio frequency identification (RFID) is used to identify, track, and manage tagged animate or inanimate objects automatically using wireless communication technology. A serious concern faced by RFID technology is the collisions that occur among tag responses when queried by a reader that limits system performance significantly. Collisions bring extra delay, a waste of bandwidth, and extra energy consumption to the interrogation process of RFID. This work extensively evaluates the performance of slotted Aloha based anti-collision protocols (that includes the current standard EPCGlobal Class 1 Generation 2) for passive tags through mathematical analysis, simulations, and practical experiments on a testbed. This comprehensive approach allows a better understanding of the theoretical and practical performance of RFID systems and the challenges that exist in improving practical performance in industrial settings. In particular, it is found that protocol mechanisms for the current standard theoretically add 10% overhead to the basic frame slotted Aloha in ideal conditions. Further, results indicate that factors like interference, antenna gain, and protocol implementation can add 50% additional delay in practical settings. This work also performs a low-level investigation of protocol behavior through power measurements and characterizes energy consumption in RFID readers.