Investigation of the effect of malfunctioned tags on the delay performance of RFID system

Radio-frequency identification (RFID) is employed for the objectives of automatically tracing and identifying the tags placed on the objects. The tags transmit their identification (ID) codes to the reader during the identification procedure and tag collision occurs when more than one tag send data to a reader simultaneously. In order to alleviate the collision problem, the EPC-Gen 2 standard uses an anti-collision protocol, known as Q algorithm, which defines that all tags shall have the capability to generate random number between 0 and 2Q-1 using a random number generator (RNG) and a 15-bit slot counter. The RFID reader can transmit a command to tags to change the Q value in order to effectively support varying load levels. After receiving the adjust command, tags will change the value of Q and then generate a new random number. In this paper, we consider the problem of malfunctioned tags when some tags violate the agree rules by not increasing the value of Q in order to achieve better delay performance than the normal tags. Simulation results show that at large number of malfunctioned tags the overall delay performance clearly degrades. Finally when comparing between the normal tags and the malfunction tags we found that the malfunctioned tags have the delay advantage over the normal tags due to a higher opportunity to be identified at the early stage of identification procedure.