Channel and Time Slot Allocation for Dense RFID Networks

This paper presents a constraint satisfaction approach to the reader collision problem in dense mode environments for static RFID networks. Our method assigns available channels and time slots to the RFID readers to increase the read rate while satisfying all the interference constraints. We model the problem with a hybrid frequency and time division multiplexing constraint satisfaction for reader anti-collision and assign workable channels and time slots to each reader using backtracking search algorithms. A depth-first-search based on backtracking was performed to find solutions to constraint satisfaction problems. Instead of performing an exhaustive search for the optimal result, we adopted good variable ordering heuristics as branching strategies where the search can be completed quickly. Thus, the search space is greatly reduced, and approximate solutions are found instantly. To find appropriate heuristics, we applied a problem classifying rule to determine the quality of the variable ordering heuristics. Computer simulations of the comparable performance of some variable ordering algorithms in the channel and time slot allocation for dense RFID networks are presented.