OSL: An optimization-based scheduler for RFID Dense-Reader Environments

© 2015 Elsevier B.V.In RFID, readers operating concurrently may interfere mutually up to distances in the order of hundreds of meters due to the extremely low power of the tag backscattered signal, causing reader-to-reader collisions. To solve this problem readers must transmit either at different times or in different channels, coordinated by means of a distributed or centralized algorithm. Centralized algorithms (schedulers) achieve the best efficiency, but current state-of-the-art proposals are still hampered by reader-to-reader collisions and idle channel phenomena, reducing performance. In this work we propose a new scheduler designed to eliminate both of these problems and to maximize throughput (number of identifications per time unit). Unlike previous schedulers, our scheduler is fed with information about the load (number of competing tags per reader) to properly compute throughput, which is expressed as a closed-form formula. At the beginning of each scheduling period our scheduler decides the channel and slots to be assigned to each reader by maximizing (with respect to these variables) the expected throughput using a simulated annealing solver. Results show that these solutions outperform state-of-the-art proposals.