Cost-effectiveness of bandwidth granularities in optical networks

Abstract

With exponential growth of users traffic demands, the efficient and cost-effective usage of bandwidth and spectrum plays an important role to improve service provisioning. This study first reviews different bandwidth granularities in optical networks. Each type of optical networks has its basic traffic unit and granularity. From this viewpoint, the optical networks are divided into fixed-grid and flex-grid networks. Fixed-grid networks (like OPS, OBS, …) have rigid nature and inflexibly assign resources to demands. However, flex-grid networks have fine nature and flexibly assign the resources to demands to avoid wasting of resources. This difference is based on modulation format. Optical frequency division multiplex (OFDM) provides superior advantages of high spectrum efficiency, robustness against inter-carrier and inter-symbol interference, adaptability to server channel conditions, and so on. An elastic optical network (EON) is a flex-grid network. One efficient type of EON is OFDM-based EON that is able to allocate the available resources in a network according to users' demands. Therefore, it makes the network more efficient and flexible. Besides, EON generates elastic optical paths (the paths with variable bit rates), and divides available spectrum flexibly according to traffic demands of clients. In this paper, the bandwidth granularity of each optical network is studied. In addition, we propose a cost model to compare the costs of SLICE networks and conventional networks. Finally, an Integer Linear Programming (ILP) is presented to tolerate the desired blocking probability, while minimizing the network cost.