Joint multiuser admission control and downlink beamforming for green cloud-RANs Via semidefinite relaxation

Cloud radio access network (Cloud-RAN) has great potentials to improve energy efficiency and increase capacity of wireless networks. In this paper, we study the green communication for Cloud-RANs. Instead of only focusing on the transmit power consumption, we minimize the network power consumption which includes not only transmit power consumption but also circuit power consumption. In addition, we take into account the scenario that some mobile users can not be served. A joint multiuser admission control and downlink beamforming scheme is proposed for Cloud-RANs to minimize the network power consumption. We first formulate the problem as a two-stage problem, and then adopt semidefinite relaxation (SDR) to transform it as a Mixed-Integer Semidefinite Program (MI-SDP) which is a convex programming when the integer variables are fixed. By using the continuous relaxation, a heuristic algorithm with low complexity is proposed to derive the suboptimal solution. The simulation results are presented to validate the effectiveness of our proposed algorithm compared with the existing work.