Joint base station activation, user admission control and beamforming in a green downlink cooperative MISO network

We consider the green communication problem in a downlink cooperative MISO network consisting of multiple base stations (BSs) and multiple users. We employ power efficiency as the performance metric, defined as the ratio of total user rate to total power consumption. The total user rate is related to the number of active users, while the total power consumption includes the transmit power and the device maintenance power, determined by the beamformers and the number of active BSs, respectively. Motivated by this observation, we consider a power efficiency maximization problem by jointly optimizing the active BSs, the admissible users and the cooperative beamform-ers. This problem is challenging due to the fractional objective and the mixed-integer program. To seek for some efficient approximate solution, we first formulate it as a convex sparse problem balancing the transmit power, the number of active BSs and the number of admissible users. A two-stage algorithm is then developed to solve the approximate problem. Simulations demonstrate the effectiveness of the proposed algorithm.