Multi-Cell Downlink Joint Transmission with 3D Beamforming

This paper proposes a scheme combining multi-cell downlink joint transmission(JT) with 3- Dimensional(3D) beamforming. The proposed scheme is based on the following two observations: 1) The performance of multi-cell joint transmission is highly dependent on the received signal strength from the coordinated cells, 2) Interference may become more severe at the cell boundary due to the extremely flat beams serving the cell edge users with 3D beamforming. In the proposed scheme, users at the cell boundary are served with JT and 3D beamforming simultaneously, and those at the cell center are served with 3D beamforming. Simulation results based on LTE-Advanced systems show that significant gains can be achieved by the scheme, with about 14% gain on cell average spectral efficiency and about 58% gain on edge user spectral efficiency compared to traditional single cell transmission with 2-Dimensional(2D) beamforming.