On the Design of Downlink Multiuser Transmission for a Beam-Group Division 5G System

Abstract

To accommodate the ever-increasing data traffic, the 5G system has adopted the enormous swathes of unlicensed spectrum at millimeter-wave band. The millimeter-wave band however exhibits orders-of-magnitude more path loss than the microwave band. The upcoming 5G system thus necessitates the use of large-scale antenna arrays to compensate for the notable path loss with beamforming gain. Nevertheless, the large number of antenna elements also poses some challenges. For example, it is impractical to assign one dedicated transceiver unit (TXRU) for each individual element and the complexity of channel estimation on spatial (antenna) domain is prohibitively high. In this paper, we design low complexity multiuser transmission on beam domain at millimeter-wave band. Specifically, we propose the beam channel set selection and user grouping schemes to significantly lower the complexity of channel estimation and precoder design by exploiting the salient feature of channel sparsity. Moreover, 2-D TXRU virtualization together with beam sweeping strategies is presented as the TXRU number is less than the number of columns of planar antenna array. Simulation results show that the proposed beam-group division 5G system can significantly reduce the complexity and keep the system throughput.