Downlink Vertical Beamforming Designs for Multi-User MISO Systems

In this paper, we study a transmit beamforming technique for multiple input single output downlink multi-user systems with directional antennas where a transmit antenna gain is determined in three dimensional coordinates. For a multiuser active antenna system, beamforming designs to maximize the weighted sum rate are proposed by optimizing the transmit antenna gain and power allocation. Since finding joint optimal parameters requires prohibitively high computational complexity, we separate the optimization problem into two sub-problems of the vertical beamforming and the power allocation. Then a simple vertical beamforming algorithm based on a high signal-to-noise ratio assumption is presented. Also, for a multi-user passive antenna system, we provide a beamforming scheme which employs a multi-sector concept. Simulation results show that the proposed beamforming schemes outperform the conventional beamforming schemes.