Sustainable Virtual Network Function Placement and Traffic Routing for Green Mobile Edge Networks

Green Mobile Edge Networks (GMENs) are emerging networks that harvest green energy for powering mobile edge nodes, thereby reducing carbon dioxide emissions and energy costs. In GMENs, network service providers can flexibly place multiple virtual network functions (VNFs) that form a service function chain (SFC) in a specific order on geographically distributed edge nodes based on the level of harvested green energy, providing customized and sustainable network services for users. To meet the diversified availability requirements of users, backup SFCs need to be provided in addition to the primary SFC. These backup SFCs can be activated for providing uninterrupted services when the primary SFC is unavailable. However, due to the dynamic nature of wireless communication links, the uncertainty and unpredictability of green energy, and the limited resources available at edge nodes, optimizing the VNF placement and route traffic in real-time is challenging to minimize energy costs of all nodes and form expected SFCs with higher availability than user demand value. In this paper, the above problem is first formulated as an integer nonlinear programming and proven to be NP-hard. Then, it is discretized into a sequence of one-slot optimization problems to handle real-time changes in green energy and link availability. Finally, an online approximation strategy with a constant approximation ratio is proposed to solve the one-slot problems in polynomial time. This is the first study into online link availability-aware VNF placement and traffic routing problems in GMENs, motivated by sustainability concerns. The evaluation results indicate that the proposed scheme can ensure service availability while reducing the energy costs of all edge nodes and has achieved better performance when compared with other state-of-the-art methods.