Dispersion Based Highest-Modulation-First Last-Fit Spectrum Allocation Scheme for Elastic Optical Networks

This paper proposes a spectrum allocation scheme based on highest modulation-first last fit (LF) for elastic optical networks in order to suppress the call blocking in the network. The proposed scheme searches the available spectrum slots from the highest indexed spectrum slots and selects the slot position with the modulation level as high as possible, which guarantees the least spectrum slots consumption. It provides higher preference of the less robust modulation technique in order to minimize the number of required slots. The last fit spectrum allocation policy is used to keep lower indexed position slots available as much as possible, which have less dispersion effect, for incoming lightpath requests and gives them the opportunity to use the less number of slots. We introduce a dispersion-based highest modulation-first LF algorithm for allocation lightpath requests. The numerical results indicate that the proposed scheme outperforms the conventional schemes in terms of blocking probability, modulation usage ratio, and average number of required spectrum slots.