UHF RFID Based Warehouse Portal In-out Registration Method

Intelligent warehouse management system (IWMS) attracts lots of interest by increasing the productivity and efficiency, minimizing the number of human workers and decreasing errors. As an important part of IWMS, warehouse portal in-out registration still face with enormous challenge. Usually, multiple UHF RFID reader antennas are installed on the portal, in-out registration can be performed by estimating the locations of RFID tags which are attached on the goods. Even though the precise localization accuracy is not required, it's still hard to distinguish the import and export directions. In this paper, we analyzed the fluctuation of received signal strength indicator (RSSI) backscattered from the RFID tags and proposed a movement direction judging method based on double-tag with an exact spacing distance. Experimental results have shown that the double-tag method can distinguish the moving direction exactly in portal environments and realize efficient in-out registration.