Energy-aware hierarchical cell configuration: From deployment to operation

This paper develops an energy-aware hierarchical cell configuration framework that encompasses both deployment and operation in downlink cellular networks. Specifically, we first formulate a general problem pertaining to total energy consumption minimization while satisfying the requirement of area spectral efficiency (ASE), and then decompose it into deployment problem at peak time and operation problem at off-peak time. For the deployment problem, we start from an observation about various topologies including the real deployment of BSs that there is a strong correlation between the area covered by an additional micro BS and the increment of ASE. Under such an assumption, we prove the submodularity of ASE function with respect to micro BS deployment and propose a greedy algorithm that is shown to be a constant-factor approximation of optimal deployment. Although the greedy algorithm can be also applied as an offline centralized solution for the operation problem, we further propose online distributed algorithms with low complexity and signaling overhead to have more practical solutions. Extensive simulations based on the acquired real BS topologies and traffic profiles show that the proposed algorithms can significantly reduce the energy consumption.