Energy-efficient cooperative downlink transmission with antenna and BS closing

Energy-efficiency (EE) has been considered as an important goal for designing future high throughput cellular networks. In this paper, we strive to improve the EE of downlink coherent cooperative transmission systems by adaptively selecting the transmitting mode, i.e., by switching off some antennas and base stations (BSs) according to the required data rate of each user and then by allocating powers to the users. To show the potential gain in EE, we first propose an optimal dynamic mode selection scheme to select the most energy-efficient active antenna and BS pattern based on the instantaneous channels, where per-user date constraint and the per-BS-power constraint are taken into account. To provide a feasible scheme for practical systems, we proceed to propose an optimal semi-dynamic mode selection scheme where the antenna and BS switching is based on the average channel gains. Simulation results with typical circuit power consumptions show that the semi-dynamic scheme performs closely to the dynamic scheme when the cell-edge signal to noise ratio is high, and both mode selection schemes provide substantial EE gain over the traditional scheme with all antennas at all BSs active.