Optimal Base Station Sleeping Control in Energy Harvesting Heterogeneous Cellular Networks

Considering a heterogeneous cellular network where macro base stations (MBSs) are powered by grid power and small base stations (SBSs) are powered by renewable energy. We investigate the grid energy minimization problem by optimizing both the MBS active probability (MAP) and the SBS transmit power (STP) under the constraints of user quality of service (QoS) and renewable energy. Using tools from stochastic geometry, we first derive the expression of the service outage probability to evaluate user QoS. And then, the impacts of the MAP and the STP on the service outage probability are characterized. At last, the optimization problem minimizing the network grid energy consumption is formulated, and the closed expressions of the optimal MAP and STP are derived by investigating the monotonicity of the service outage probability. Numerical results show that our strategy of jointly optimizing the MAP and the STP is superior to the strategy of merely considering MBS sleeping with fixed SBS transmit power, and the superiority is more attractive with lower circuit power of SBS.