Improving Energy Efficiency of Cooperative Femtocell Networks via Base Station Switching off

Recently, energy efficiency (EE) of cellular networks has become an important performance metric, and several techniques have been proposed to increase the EE. Among them, turning off base stations (BSs) when not needed is considered as one of the most powerful techniques due to its simple operation and effectiveness. Herein, we propose a novel BS switching-off technique for cooperative femtocell networks where multiple femtocell BSs (FBSs) simultaneously send packets to the same mobile station (MS). Unlike conventional schemes, cooperative operation of FBSs, also known as coordinated multipoint (CoMP) transmission, is considered to determine which BSs are turned off in the proposed technique. We first formulate the optimization problem to find the optimal set of FBSs to be turned off. Then, we propose a suboptimal scheme operating in a distributed manner in order to reduce the computational complexity of the optimal scheme. The suboptimal scheme is based on throughput ratio (TR) which specifies the importance of a particular FBS for the cooperative transmission. Through simulations, we show that the energy consumption can be greatly reduced with the proposed technique, compared with conventional schemes. Moreover, we show that the suboptimal scheme also achieves the near-optimal performance even without the excessive computations.