Green Multicell Cooperation in Heterogeneous Networks With Hybrid Energy Sources

Concerns with global warming have prompted much research effort in energy-related issues for cellular systems. Heterogeneous networks (HetNets) incorporated with small cells save energy effectively due to the lower transmit and operational power consumptions of small cells. Multicell cooperation employing both cooperative transmission to tackle inter-cell interference and sleep mode operation to attain network energy conservation plays a decisive role in future green HetNets. Energy harvesting is another trend to achieve network energy savings. In this paper, we investigate how green multicell cooperation (GMC) can be achieved in HetNets facilitated with hybrid energy sources. Due to the lack of efficient solution approaches in coping with the spatial and temporal characteristics of the GMC problem simultaneously, we propose a greedy decomposition to solve the GMC problem via two sub-problems. We prove that the achieved grid energy consumption can be upper bounded, and observe that the tightness of the upper bounds hinges on two clustering-related factors, which may guide the scheduling design in future green HetNets. Our simulation results show that the proposed solution outperforms the existing approaches in terms of grid energy savings, and also demonstrate the cluster formation results and the dynamics of the clustering-related factors.