Time-Aware Routing and Spectrum Assignment Assisted by 3D-Spectrum Auxiliary Graph in Elastic Optical Networks

With setting up and tearing down of dynamic requests, there will inevitably be spectrum fragmentation in elastic optical networks, leading to a higher blocking ratio. However, conventional algorithms only consider current spectrum fragmentation in the 2D-spectrum auxiliary graph, which determines whether requests can be accepted when they arrive. To overcome this problem, we propose an innovative routing and spectrum assignment algorithm considering the future fragmentation, which determines whether requests can be accepted when other online requests leave. In this algorithm, we first introduce a time variance metric to measure the occupied holding time of both the current request and its adjacent online requests, and then propose a model with the minimal time variance in the 3D-spectrum auxiliary graph, which tries to ensure all the leaving time is similar around the current requests. Finally, we verify the advantages of the proposed algorithm in terms of blocking ratio, fragmentation ratio, and spectrum utilization ratio through simulation results.