A RFID system's front-end consists of multiple tags being identified by a single (or multiple) reader. In order for the reader to uniquely identify all tags within certain range, some sort of anticollision mechanism is required. ALOHA and its variations can be used in such a scenario. EPC Global, a standardizing body for RFID technology, has proposed a Dynamic Framed Slotted ALOHA mechanism for UHF passive tags (Gen 2, Class I), and a 'Q' algorithm is used to dynamically update the size of the frame, where the size changes exponentially. Two parameters that define this Q algorithm are the initial size of the frame and the speed of frame-size estimation. In this paper we present a complete RFID system simulator which can be used to investigate various algorithms in various scenarios, in context of UHF RFID systems, and then present our simulation setup, results and analysis where the throughput for different traffic scenarios is calculated. Based on the results the trend and the optimal values are discussed for the two parameters. These results can be used by an RFID system designer to choose the right initial parameters, based on an order-of-magnitude estimate of the traffic conditions. © 2012 IEEE.