[Proceeding] Power-Aware Routing and Wavelength Assignment in Optical Networks

We introduce the Power-Aware RWA problem, whose goal is to accommodate lightpaths in wavelength routing networks minimizing the power consumption. Formulation, algorithms, and results are presented, showing that significant power savings are possible. Introduction Wavelength Routing (WR) networks offer the flexibility of designing a “logical topology”, comprising lightpath requests, over a physical topology, comprising OXCs and links with many fibers each. The Routing and Wavelength Assignment (RWA) problem is well known in the literature [1]. Its goal is to assign a route and a suitable wavelength in the physical topology for each lightpath of the logical topology. Traditionally, the goal of the RWA problem is to minimize the load (e.g., number of wavelengths) on available resources, in order to maximize the probability of accommodating possible new lightpath requests. However, this leads in general to a waste in the power required to keep up and running both OXCs and optical amplifiers along fiber links. Given the large number of these devices (thousands) and their power footprint (up to tens of kW), we propose to target the minimization of power consumption when solving the RWA problem, by making maximum usage of powered-on devices, e.g., by reusing the same fiber along the same path as much as possible, in contrast to spreading lightpaths on available fibers and paths. We name this problem Power-Aware RWA (PA-RWA) problem. In this paper, we give a formulation of the problem, propose heuristics to solve it, and present simulation results showing that a large amount of power can be saved in WR networks, reducing up to a factor of 5 the energy (and the cost) needed to operate a WR network. Problem Formulation The PA-RWA problem can be defined using an integer linear programming (ILP) formulation. Let Λsd denote the number of lightpath requests from source s to destination d, and λsdw the number of lightpaths from s to d on wavelength w: Λsd = ∑ w λsdw. Let f sdw ijk ∈ {0, 1} denote the number of lightpaths from s to d on fiber k of link (i, j) using wavelength w, and f ij = ∑ k f sdw ijk . On link (i, j), let Kij be the number of fibers, and Fijk the number of wavelengths available on fiber k. Let aijk be the number of amplifiers on fiber k of link (i, j), and xijk ∈ {0, 1} be binary variables equal to 1 if fiber k on link (i, j) is used to route a lightpath. Similarly, let yi ∈ {0, 1} be binary variables equal to 1 if OXC i is used. Finally, let PA and PO be the power consumptions of one amplifier and one OXC, respectively. We do not consider the possibility of powering off individ∗This work was partially supported by the BONE research project. ual transceivers or subsystems in OXCs. The notation above leads to the following ILP formulation of the PARWA problem: minPtot; Ptot = PA ∑ i,j,k aijkxijk + PO ∑