Heterogeneous Beamspace Design for 5G Millimeter-wave Systems

In the last years, the interest on millimeter wave communications increased due to the high potentiality foreseen to face the continuous growth of wireless communications capacity demand. One of the major drawback is represented by the limited coverage capacity. In order to cope with it, beamformers that generate beams with very narrow beams have been studied. Special attention has to be devoted to the tradeoff between coverage distance and area covered by the beam: depending on the UEs deployment, a too narrow beam might result into a low throughput and spectrum efficiency. In this paper a new solution to improve the cell coverage and the spectrum efficiency is proposed. The idea is based on the fact that the beamformers are designed to be flexible to choose the beam from a codebook of beams with different widths and different directions. The choice depends on a scheduling algorithm designed to maximize the performance of the system.