Energy-Minimized Design and Operation of IP over WDM Networks with Traffic-Aware Adaptive Router Card Clock Frequency

With the explosive expansion of the information and communication technology (ICT) section, its energy saving has become an important issue and is receiving wide interest. In this study, we propose an adaptive clock frequency strategy for router cards to minimize the total energy consumption of an IP over WDM network. Rather than always running at full speed, the clock frequency of a router card is adaptively adjusted according to its actual-carried traffic demand. Given forecast traffic demand matrixes between different node pairs in different time slots, we develop a mixed integer linear programming (MILP) model to optimally choose the clock frequencies for each router card in different time slots such that the total energy consumption of the router cards is minimized. For lower computational complexity, the optimization model is also decomposed into two models, which correspond to the two subproblems of the optimization problem. The first subproblem minimizes the total number of router cards at each network node based on the peak-hour traffic, and the second subproblem optimally chooses the clock frequencies for each router card in different time slots. Due to the high-computational complexity of the MILP models, we also develop an efficient heuristic algorithm, in which two key steps that tackle the two subproblems are specifically developed. The joint MILP model provides a lower bound on the energy consumption, which shows to save more than 40% energy compared to the case without adaptive router card clock frequency. It is also found that the heuristic algorithm is efficient and performs close to the MILP models. In addition, the results also show that a router card supporting a small number of discrete clock frequencies can perform close to a card with continuously changed clock frequencies, and the benefit of adaptive clock frequency becomes weak with increasing router card power consumption overhead.