A centralized and aligned scheduler for passive RFID dense reader environments working under EPCglobal standard

Passive RFID systems with several reader stations densely allocated close to each other are susceptible to reader collision problems. They are characterized by reader-to-tag and reader-to-reader interferences. Both degrade the system performance, decreasing the number of tags identified per time unit. Although some proposals have been suggested to avoid/handle these collisions, most of them require extra hardware, do not make an efficient use of the network resources and are not compatible with the current standards and regulations. This paper proposes a centralized and aligned scheduler that optimizes the distribution of network resources (frequencies and time slots) among the readers in the network. Those readers with unidentified tags in their target region will have higher priority for receiving resources. The optimization problem is formulated as a Mixture Integer Programming problem. Results show that the method proposed provides higher network throughput and fairness than the EPCglobal Class-1 Gen-2 standard for dense reader environments. In addition, unlike previous works, the scheduling algorithm presented is compatible with EPCglobal standard and the European regulation, and can be implemented in real RFID systems with fixed and mobile readers.