Joint base station activation, user admission control and beamforming in downlink green networks

Consider a multicell downlink network, where the base stations (BSs) in different cells cooperate in the precoder level, while those in the same cell are coordinated for joint processing UP). To achieve green communication, we optimize the network power consumption under some quality-of-service (QoS) constraints. Different from the conventional approaches based on BS activation and beamforming, we further integrate user admission control into network management, and thus minimize the power consumption by jointly optimizing the active BSs, the admissible users and the transmit beamformers. This strategy has two advantages. First, it ensures that the network still works even when some users cannot achieve the QoS requirements. Second, it helps select a subset of users whose QoS requirements can be satisfied with relatively low power cost, thereby improving the power efficiency. However, this problem is challenging due to the mixed-integer programming. To pursue some efficient approximate solution, we first reformulate it as a convex sparse optimization problem and then develop a distributed algorithm to iteratively solve the problem, utilizing the alternating direction method of multipliers (ADMM). The proposed algorithm has very low complexity since each step can be computed in closed form. Its efficacy and efficiency are demonstrated by numerical simulations. (C) 2017 Elsevier Inc. All rights reserved.