An Accurate Tag Estimate Method for Improving the Performance of an RFID Anticollision Algorithm Based on Dynamic Frame Length ALOHA

In a radio-frequency identification (RFID) system, the dynamic frame length ALOHA protocol is widely adopted to solve the anticollision problem. Analysis for the anticollision problem can be divided into two primary parts. The concern of the first part is how to precisely estimate the number of tags. The other part involves determination of dynamic frame length to achieve maximum throughput or channel usage efficiency. In this paper, we present an accurate method for estimating tag quantity. This method is based on the maximum a posteriori probability decision. We also derive the optimal frame length using radio channel efficiency. Simulation results indicate the tag estimate error of the proposed method is less than 4%. Use of our proposed tag estimate method together with optimal frame length can achieve close to the theoretical maximum throughput of the framed ALOHA algorithm. Note to Practitioners-A tag estimate method presented here is capable of precisely estimating the number of tags in resolving multiple-tag access using dynamic frame length ALOHA. The optimal frame length for obtaining the maximum radio channel efficiency is derived. Performance measures including tag estimate error and total read time show that our proposed anticollision algorithm is superior in comparison to previously published work. Since the frame length update mechanism including tag estimate method and the setting of frame length is not specified in current RFID standards such as ISO 18000-6 and ISO 14443-3, our proposed anticollision algorithm can be useful for engineers to implement the dynamic frame length ALOHA algorithm in a real RFID system. Also, using our method can achieve uplink throughput close to the theoretical maximum value 0.368 of the framed ALOHA algorithm.