In this paper, we consider the precoder design for an underloaded or critically loaded downlink multi-user multiple-input multiple-output (MIMO) communication system. We propose novel precoding and decoding schemes which enhance system performance based on rate splitting at the transmitter and single-stage successive interference cancellation at the receivers. The proposed successive null-space (SNS) precoding utilizes linear combinations of the null-space basis vectors of the successively augmented MIMO channel matrices of the users as precoding vectors to adjust the inter-user-interference experienced by the receivers. We formulate a non-convex weighted sum rate optimization problem for the precoding vectors and the associated power allocation for the proposed SNS-based MIMO-rate-splitting multiple access (RSMA) scheme. We obtain a suboptimal solution for this problem via successive convex approximation. Moreover, we study the robustness of the proposed precoding scheme to imperfect channel state information (CSI) at the base station via derivative-based sensitivity analysis. Our analysis and simulation results reveal the enhanced performance and robustness of the proposed SNS-based MIMO-RSMA scheme over several baseline multi-user MIMO schemes, especially for imperfect CSI.
翻译:在本文中,我们考虑过一个载量不足或重装入下行的多用户多投入产出(MIMO)通信系统的预编码设计;我们提出新的预编码和解码计划,根据发射机的分率和接收器的单阶段连续干扰取消,加强系统性能;拟议的连续连续无空间(SNS)预编码利用连续增加的MSIMO频道通道矢量的无空间矢量的线性组合,作为预先编码的载体,以调整接收器所经历的用户相互干预。我们为预先编码的矢量设计了一个非编码加权总和优化问题,并为拟议的以SSNS为基础的多位访问(RSMA)计划及相关的动力分配问题提出了非编码总和加权优化问题。我们通过连续的 convex近距离,为这一问题找到一个亚优的解决方案。此外,我们研究了拟议的预先编码计划对于基础站的不完善的频道国家信息(CSI)的稳健性,通过基于衍生物的敏感度分析来调整。我们的一些分析和模拟结果揭示了SNS-MSIMIMA的拟议基线计划,特别是不完善的MSIMIMIMA基准计划。