OPS/OBS scheduling algorithms: Incorporating a wavelength conversion cost in the performance analysis

With ever-increasing demands for bandwidth optical packet/burst switching is used to utilise more of the available capacity of optical networks. In current prototypes of optical switches time and wavelength multiplexing are combined to resolve packet contentions by means of Fiber Delay Lines and wavelength converters in the switching elements. Although optical switches have lower energy consumption than their electronic counterparts, it remains substantial. Since wavelength converters contribute significantly to the switches overall energy consumption, they should be used sparingly, rather than continuously. Current scheduling algorithms however do not take the usage of wavelength converters (and the related energy consumption) into account. To this end, we developed and evaluated new cost-based scheduling algorithms, which take both gap and delay into account to schedule an incoming packet. The performance improvement of these algorithms over existing algorithms can be traded off for a significant reduction in up-time of the wavelength converters by introducing a conversion cost in the involved cost function. This is backed by Monte Carlo simulation results, in which the algorithms are applied both in a void-filling and non-void-filling setting. The algorithms are of the same implementation complexity as current algorithms, and thus of immediate value to switch designers.