ALOHA algorithm considering the slot duration difference in RFID system

when multiple RFID tag identification is becoming a commonplace, the anti-collision technology for multiple RFID tag environment has drawn mounting research interest in the RFID domain. Many published Aloha-based algorithms, assuming that all the slots have the same duration, tend to increase the number of successful slots by tag estimation and dynamic frame scheduling, and thus improve the system efficiency (the ratio of successful slots to all slots in each frame), which is limited by 1/e according to the theory of Probability. Whereas, in this paper, the effect of the empty slots and collided slots is analyzed and two novel methods based on the parameters of EPC Gen2 protocol, BIS and Collision Detection, are proposed, to improve the RFID system efficiency by reducing the cost of the none successful slots other than the successful slots. Moreover, a new approach to evaluate the system efficiency for multiple tag identification, taking consideration of the duration difference of the slots, is presented. According to the simulation and test results, the proposed methods, BIS and Collision Detection, can improve the system throughput by 120% and 30~40% respectively.