The challenge of optimal Routing and Spectrum Assignment (RSA) is significant in Elastic Optical Networks. Integrating adaptive modulation formats into the RSA problem - Routing, Modulation Level, and Spectrum Assignment - broadens allocation options and increases complexity. The conventional RSA approach entails predetermining fixed paths and then allocating spectrum within them separately. However, expanding the path set for optimality may not be advisable due to the substantial increase in paths with network size expansion. This paper delves into a novel approach called RMLSA, which proposes a comprehensive solution addressing both route determination and spectrum assignment simultaneously. An objective function named ABACUS, Adaptive Balance of Average Clustering and Utilization of Spectrum, is chosen for its capability to adjust and assign significance to average clustering and spectrum utilization. Our approach involves formulating an Integer Linear Programming model with a straightforward relationship between path and spectrum constraints. The model also integrates Physical Layer Impairments to ensure end-to-end Quality of Transmission for requested connections while maintaining existing ones. We demonstrate that ILP can offer an optimal solution for a dynamic traffic scenario within a reasonable time complexity. To achieve this goal, we adopt a structured formulation approach where essential information is determined beforehand, thus minimizing the need for online computations.

翻译：在弹性光网络中，最优路由与频谱分配（RSA）问题具有重要挑战。将自适应调制格式整合至RSA问题——即路由、调制等级与频谱分配（RMLSA）——拓宽了分配选项并增加了复杂度。传统RSA方法需预先确定固定路径，再在这些路径内分别进行频谱分配。然而，随着网络规模扩展，路径数量大幅增加，扩展路径集以实现最优性可能并不可取。本文深入探讨一种名为RMLSA的新方法，该方法提出同步解决路由确定与频谱分配的综合性方案。我们选定名为ABACUS（平均聚类与频谱利用的自适应平衡）的目标函数，因其能够调节并赋予平均聚类与频谱利用以重要性。本文方法构建了一个整数线性规划模型，该模型在路径与频谱约束之间建立简洁关系。该模型还整合了物理层损伤因素，以确保为请求连接提供端到端传输质量，同时维持现有连接。我们证明，在合理时间复杂度内，ILP可为动态流量场景提供最优解。为实现此目标，我们采用结构化建模方法，预先确定关键信息，从而最大程度减少在线计算需求。