Energy saving and cost reduction in multi-granularity green optical networks

With the energy consumption increase and the greenhouse effect becomes more and more serious, the energy saving has become the focus in the whole world. At the same time, as the network traffic largely growing, the size and the cost of network equipments keep increasing so that the network cost reduction is also very important. In recent years, the concept of green Internet was proposed to construct an energy-efficient and cost-optimal green network. In this paper, we firstly present the current studies working on the energy saving and cost reduction in multi-granularity optical network that is the convergence between IP network and optical network to support both the low-speed IP data and the high-speed optical transmission. After analyzing the current studies, in our opinion, the traffic grooming mechanism with optical bypass technology is the feasible solution by binding a lot of low-rate IP data into a few of high-speed lightpaths to reduce a lot of electrical ports consumption in IP routers for saving the energy, the waveband switching mechanism is the feasible solution by binding multiple lightpaths into a few of waveband tunnels to save the optical transmitting ports consumption in Multi-Granularity Optical Cross-Connects (MG-OXCs) for reducing the network costs, and the multi-granularity grooming mechanism is the feasible solution by integrating the traffic grooming with the waveband switching to achieve both the energy saving and cost reduction. Based on our opinion, this paper proposes the challenging issues including the network node model, virtual topology design, certain traffic matrix and uncertain traffic matrix for energy saving and cost reduction in multi-granularity optical network, with possible solutions and preliminary simulation results to guide the future work.