Resource Management in Sustainable Green HetNets with Renewable Energy Sources

Green energy has become a promising alternative energy source for powering wireless cellular networks by effectively reducing the network operational expenditure (OPEX) and carbon footprints. However, green energy sources such as solar and wind are harvested from the environment and their availability and capacity are by nature unstable, which poses great challenges to achieve sustainable network operation. In this chapter, we study the energy sustainable performance of a green HetNet where the small cell base stations (SBSs) are powered by green energy sources. Specifically, we first develop an analytical framework to study the energy sustainability of each SBS. The energy buffer at each SBS is modeled as a G/G/1 queue with arbitrary patterns of energy charging and discharging. We apply the diffusion approximation to analyze the transient evolution of the energy buffer, and derive the probability distribution of the queue length and the energy depletion time for a given initial energy level. Based on the energy sustainability analysis, we propose a distributed admission control strategy at SBSs striking a balance between high resource utilization and energy sustainability in the green HetNet. Extensive simulations are conducted to validate the analytical framework and evaluate the sustainability performance of the green HetNets using the proposed distributed admission control scheme. The simulation results demonstrate that relaxing the admission control criteria for the SBSs can improve the resource utilization (i.e, power and spectrum) of the system when the energy is abundant, but can significantly degrade the resource utilization instead when the energy comes short due to poor sustainability performance (i.e., frequent depletion of the SBSs).