ILP models and improved methods for the problem of routing and spectrum allocation

Elastic Optical Networks (EONs) using a flexible wavelength allocation technique with smaller granularity of spectrum can improve the efficiency and flexibility for diverse traffic transmission. However, due to the small granularity in EONs, the resource allocation problems become more complicated than that of the existing network architecture. By classifying the integer linear programming (ILP) models for solving the resource allocation problem on EONs into four categories, i.e., path/slot, path/channel, node/slot and node/channel, the characteristics of each are reviewed and tighter lower bounds estimation schemes for these ILP models are designed. Also, for channel models (i.e., path/channel and node/channel models), we propose two improved channel generation methods in pre-processing to reduce the number of variables. In the comparative experiments, we show the superiority of our methods, and by using them, analyze the characteristics of the four models.