Optimal packet scheduling in output-buffered optical switches with limited-range wavelength conversion

All-optical packet switching is a promising candidate for future high-speed switching. However, due to the absence of optical Ran-dom Access Memory, the traditional Virtual Output Queue (VOQ) based input-queued switches are difficult to implement in optical domain. In this paper we consider output-buffered optical packet switches. We focus on packet scheduling in an output-buffered optical packet switch with limited-range wavelength conversion, aiming at maximizing throughput and minimizing average queuing delay simultaneously. We show that it can be converted to a minimum cost maximum network flow problem. To cope with the high complexity of general network flow algorithms, we further present a new algorithm that can determine an optimal scheduling in O (min {W²,BW}) time, where W is the number of wave-length channels in each fiber and B is the length of the output buffer. We also conduct simulations to test the performance of the proposed scheduling algorithm under different traffic models.