Dynamic Framed Slotted ALOHA Algorithm Used in RFID System

In radio frequency identification(RFID) systems,one of the most widely used anti-collision algorithms is the dynamic framed slotted ALOHA(DFSA)algorithm which usually uses two methods,one is tag estimation method (TEM) which estimates the number of tags around the reader,and the other is dynamic slot allocation (DSA) method which is the method to dynamically allocate the frame size according to the number of tags.DFSA can achieve optimal system performance when the frame size is equal to the number of tags.As the number of tags becomes large,DFSA is not practical to increase the frame size infinitely,thus the application of DFSA algorithm is limited.In this paper a TEM method and a DSA method are proposed from two novel aspects respectively in order to use DFSA algorithm more effectively,and the analysis and comparison are given subsequently.Meanwhile,the improved DFSA algorithm is proposed to solve the problem of DFSA algorithm.When the number of tags is large,if the improved DFSA algorithm is applied,the system efficiency that can be attained is not less than 50%.