NFV-enabled optimal spectrum allocation in flex-frid optical networks

© 2020 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.This paper proposes an NFV-Enabled optimal spectrum allocation solution applicable to fixed-grid and flex-grid wavelength division multiplexing (WDM) optical networks. By exploiting the frequency shifting capability of individual lightpaths, the proposed approach aims to recalculate the initial spectrum allocation to eliminate the unusable gaps between occupied frequency slots. The reorganized spectrum will facilitate the allocation of new connections, in order to enable the maximization of spectrum utilization. In this regard, this paper describes the NFV-enabled scheme for carrying out the optimal spectrum allocation. The optimization problem is formulated as an Integer Linear Program (ILP) model and solved optimally using an exact brute-force search-based algorithmic strategy (OptFs). Given the NP-hard nature of the optimization problem and the non-polynomial complexity of OptFs, a suboptimal, faster heuristic strategy (FastFs), based on a prepartition method, is proposed. Simulation results validate the performance of the proposed optimal spectrum allocation approach, and the exact and heuristic solutions, compared to the non-application of strategies, demonstrate improvements in spectrum utilization while offering a dynamic network operation.This work has been supported by the Ministerio de Economía y Competitividad of the Spanish Government under project PID2019-108713RB-C51. Christian Tipantuña acknowledges the support from Escuela Politécnica Nacional and from SENESCYT for his doctoral studies at UPC.Peer ReviewedPostprint (published version