Allocation of time slots for RFID readers so as to avoid collision has been an active research problem in recent years. Various techniques have been proposed and demonstrated with success in small scale reader networks. In this paper, a heuristic algorithm and three simulated annealing (SA) algorithms for solving this problem are studied. Clearly, heuristic algorithm converges faster to a local solution than the SA algorithms. However, SA algorithms provide slightly better solution in terms of the number of time slots required for collision free interrogation.