Efficient Richardson iteration of null-space expansion for multi-user massive MIMO in time-varying channel

Abstract This paper focuses on a low-complexity precoding weight suitable for multi-user massive multiple-input multiple-output (MU-mMIMO) in user equipments’ (UEs’) mobility environment. Null-space expansion (NSE) method achieves better inter-user interference (IUI) suppression performance than channel prediction schemes by steering several nulls for interfering UTs in the high mobility environment. However, NSE faces challenges in effectively managing the computation complexity of the weight design. In this work, we incorporate a Richardson iteration (RI) in zero-forcing (ZF)-based NSE method to reduce computation burden. Moreover, deep-unfolding (DU) is utilized to further accelerate the convergence of RI-based NSE method. Computer simulation demonstrates the superiority of the proposed scheme in terms of IUI suppression performance and computation complexity.