Abstract
A fragmentation-avoiding spectrum assignment strategy based on spectrum partition is proposed, which is used to resolve the spectrum fragmentation problem in elastic optical networks. For alleviating spectrum fragmentation, a spectrum partition policy, splitting the whole optical spectrum into several dedicated partitions, is presented. Based on this, a joint first-last-fit spectrum assignment policy is presented to enhance the probability of successful transmission of request and spectrum efficiency, where each partition is first used to transmit requests with the same rate in the first-fit policy; and other partitions are used to search available spectrum resources in the last-fit policy when there are no available spectrum resources in the dedicated partition. Meanwhile, a partition selection formula is designed to minimize the interference of spectrum resources during the last-fit spectrum assignment. Moreover, a reconfiguration mechanism, moving requests that are not transmitted in their dedicated partition to their dedicated partition, is also studied. The simulation results indicate that the proposed algorithm can reduce the bandwidth blocking probability and improve spectrum efficiency.
Highlights
With the rapid development of the Internet, there have come into being a variety of bandwidth intensive applications, such as video conference, high definition television and cloud computing
The major contributions of our work are the following. i) By considering the size and arrival rate of all requests, we propose a novel spectrum partition policy; each partition is first used to transmit requests with the same rate in the first-fit (FF) spectrum assignment policy. ii) We propose a last-fit (LF) spectrum assignment policy having a temporary loan to other partitions, and design a partition selection formula, which enhance the probability of successful transmission of request and reduce spectrum fragmentation (SF). iii) A reconfiguration mechanism, moving these requests that are not transmitted in their dedicated partition to their dedicated partition, is studied
We investigate the spectrum fragmentation problem caused by mixed line rate requests provisioning for Elastic optical networks (EONs)
Summary
With the rapid development of the Internet, there have come into being a variety of bandwidth intensive applications, such as video conference, high definition television and cloud computing. Elastic optical networks (EONs) use much finer granularity (e.g., 12.5 GHz or even 6.25 GHz) and bandwidth-variable optical devices to establish lightpath [5], which significantly improves flexibility and efficiency of spectrum assignment in the optical layer. On the spectrum assignment aspect, the establishment of lightpath is limited to the above spectrum constraints Both of these factors have brought a new challenge to EONs, that is, spectrum fragmentation (SF) problem [7]–[9]—spectrum resources are cut into several discrete and different-sized SFs. As a consequence, compared with low rate requests, it is harder to find available spectrum resources for high rate requests, which reduces spectrum utilization ratio (SUR) and indirectly increases the probability of request blocked.
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