An iterative interference replica subtraction approach for low-complexity precoding in multiuser massive MIMO null-space expansion

Abstract This paper proposes a novel precoding weight that reduces computational cost and enhances inter-user-interference (IUI) suppression performance in time-variant multi-user massive multiple-input multiple-output (MIMO) environments. In multiuser MIMO transmission, channel variations degrade IUI suppression performance of the precoding weight. Null-space expansion (NSE) was developed as one of the promising precoding designs to maintain effective null-steering to the future channel state of interfering user terminals (UTs). Meanwhile, massive MIMO system requires high computation resources due to the large number of antennas. Iterative interference replica subtraction (IIRS) reduces the complexity for the calculation of the precoding weight and provides a computationally efficient solution. Our proposed precoding weight integrates NSE and IIRS to address the above both challenges. We demonstrate significant improvements in computation efficiency and interference suppression under time-variant conditions through the computer simulation. The effectiveness of the proposed IIRS-NSE becomes particularly evident in scenarios with a small expansion factor and UTs’ high mobility environment.