Energy efficiency and CAPEX minimization for backbone network planning: Is there a tradeoff?

Energy efficiency and the minimization of capital expenditures (CAPEX) for network equipment are studied for two network architectures: IP over WDM and IP over OTN over WDM. Case study results from mixed integer linear programming (MILP) formulations indicate that a CAPEX optimized network yields solutions having minimum energy consumption for both architectures. However, it is shown that the most cost efficient architecture is not always the least energy consuming. We quantify the occurring tradeoff and observe that network equipment CAPEX are dominating in terms of cost. Additionally, it is observed that the relative power contribution of different network layers is independent of the average inter-node traffic demand for both studied architectures.