Resource Allocation for Energy Saving in Downlink Wireless Communication with Direction-Variable Antennas

The directional antenna provides energy focusing in a specific direction, therefore becoming an effective energy-saving solution. In this paper, we consider energy saving problem in a further way by resource allocation in base station equipped with direction-variable antennas. Besides the total power limitation and the total time slot limitation, the concurrent transmissions are also limited by the amount of directional antennas. Within these limitations, we jointly perform the power allocation, the time allocation and the user selection, which is different from the other energy-saving works. We explore the influence of user selection on the resource utilization and propose the concept of selectivity advantage. A state decomposition model is then proposed to exploit the combination gain, and also simplify the inherent complexity of the joint design problem. But its parameters are coupled, therefore the explicit solution cannot be obtained through the convex optimization algorithm. A suboptimal solution, named Time Refund based Resource Allocation algorithm (TRRA), is proposed and simulations show that the proposed method outperforms the non-joint allocation algorithm in energy saving, especially in the case of large amount of users.