Efficient adaptive vertical downtilt schemes in LTE-Advanced networks

This work introduces efficient schemes for adaptive vertical downtilt beamforming in Long Term Evolution Advanced (LTE-A) networks equipped with active antenna systems (AAS). A framework to determine cell-specific downtilt angles is proposed and solutions are provided with affordable complexities for practical applications. Instead of utilizing a single fixed downtilt, a cell-specific downtilt is obtained and adaptively adjusted across the system, which not only increases signal strength for desired users but also provides better control of inter-cell interference in the system. System level simulation shows that the proposed schemes achieve up to 10% cell edge and 5% cell average spectrum efficiency gain compared to the baseline system with fixed downtilt without involving complex coordination among cells.