Energy-efficient design of heterogeneous cellular networks from deployment to operation

The ever-increasing traffic demand has motivated mobile operators to explore how they can boost their network capacity with a minimal increase in their capital and operating expenditures. In order to tackle this problem, we investigate the energy-efficient design of heterogeneous cellular network (or simply HetNet), especially with a focus on deployment and operation strategies. We first formulate a general problem pertaining to minimizing the total energy consumption cost while satisfying the requirement of area spectral efficiency (ASE). We decompose this problem into a deployment problem at peak time and an operation problem at off-peak time. Under practical assumptions made from an observation on various topologies including an acquired real base-station deployment dataset, we demonstrate the submodularity of ASE function with respect to micro base-station deployment. Subsequently, we propose a greedy algorithm that is shown to be a constant-factor approximation to the optimal deployment. Although the greedy algorithm can be applied as an offline centralized solution for the operation problem, we further propose two online distributed algorithms with low complexity and signaling overhead using Lagrangian relaxation technique. Extensive simulations show that the proposed algorithms can significantly reduce the energy consumption with minimal deployment of micro base-stations.