Abstract
RFID technologies have been applied in various applications such as inventory control and supply chain management. In this paper, we investigate the tag searching problem in large RFID systems containing multiple readers. Given a particular set of wanted tags, tag searching refers to finding which of them present in the system. Tag searching is important to many practical applications and it should be done quickly. Prior researches on tag searching did not consider interference among nearby readers, which will greatly affect the time efficiency of tag searching solutions. In this paper, we propose a tag searching protocol that achieves high time efficiency by jointly optimizing the searching precision and reader scheduling. We propose a novel technique to quickly test whether a wanted tag exists in the system or not. The execution time of the protocol is greatly affected by the scheduling of readers. We formulate the minimum time reader scheduling problem and prove its NP-hardness. We then design a heuristic algorithm to find a feasible reader scheduling. Simulation results show the superior performance of the proposed searching protocol: Compared with the best existing solutions, the proposed protocol reduces execution time by more than 40 percent.