Multi-user hybrid precoding design based on QR decomposition and beam gain alignment

Abstract

Millimeterwave massive MIMO systems based on lens antenna arrays can effectively reduce the number of required RF chains without loss of performance. In order to solve the problems of leakage power and multiuser interference in existing beamspace channels, a hybrid precoding scheme was proposed that combining QR decomposition and beam gain alignment (BGA). Firstly, a phase shift network (PSN) structure was designed, so that each RF chain in beamspace MIMO can select multiple beams to collect the leakage power. Secondly, QR decomposition was performed on the beam channel matrix, with the achievable sum rate as the goal, and appropriate beams were selected one by one in increasing order until the optimal beam selection matrix was selected.Finally, the beam gain alignment (BGA) strategy was used to design the analog precoding. In order to eliminate multiuser interference in the system, a digital precoder was designed to diagonalize the channel. Simulation results show that the proposed algorithm has lower complexity and higher achievable sum rate and energy efficiency.

Keywords

• massive MIMO
• hybrid precoding
• QR decomposition
• beam gain alignment
• multiuser interference