Scheduling algorithms for shared fiber-delay-line optical packet switches - The single-stage case

Optical packets may arrive at an optical switch in an uncoordinated fashion. Therefore, fiber delay lines (FDLs) are needed to buffer packets when contention occurs. There have been several optical-buffered switch architectures and FDL assignment algorithms proposed in the literature. However, most of them either have high implementation complexity, or fail to schedule departure time for delayed packets. In this paper, we study the scheduling algorithms for the single-stage shared-FDL optical packet switch. We propose two new FDL assignment algorithms: the sequential FDL assignment (SEFA) algorithm and the multi-cell FDL assignment (MUFA) algorithm. Our algorithms can make resource reservation so as to schedule departure time for packets. Owing to FDL and/or output-port conflicts, the packets that fail to be scheduled are discarded before entering the switch. We show by simulation that with these algorithms, the optical-buffered switch can achieve a loss rate of ∼10 ^-7 even at the load of 0.9.