Partial defragmentation in elastic optical networks

In elastic optical networks, the lightpaths setup and tear down processes may cause the so-called spectrum fragmentation issue, degrading spectrum utilization, increasing lightpath rejection ratio, and this is especially critical under dynamic traffic scenarios. In this letter, we first theoretically analyze the lightpath rejection ratio in elastic optical networks and reveal the relationship between link utilization and the rejection ratio. Then a novel link-based partial defragmentation method which could effectively reduce lightpath rejection ratio and reduce reconfiguration is proposed. Simulation results show that the proposed scheme may reduce up to 40% lightpath reconfigurations comparing to traditional defragmentation schemes.